Question: Polafish

Comment on Polafish

Hey, how come the salinity of the stretch of downstream river from a "desalinisation" plants increases? Isn't' a dealinatisation kind of plant used to decrease the salinity of a stretch of water?!I don't have any problem in identifying the one statement that strengthens the argument the most, but I do have this minor problem with how the two premises are connected in the first place.
gmat-admin's picture

The desalinization plant isn't there to remove salt from the river, It's there to remove salt from pretzels ("pretzel desalinization plant"). I know there's no such thing as a pretzel desalinization plant (yet!). The term is somewhat tongue-in-cheek. So, once the plant removes the salt from pretzels, it appears that some of the salt is making its way into the river.

Haha, this is a funny one. The silicon valley yuppies are surely working on such an idea and will receive much needed seed funding.

Hello Brent .... Need help on this one. How is E an answer ?

According to me if certain Climatic conditions follow the outbreak does it not mean its too late to use the Vaccine as the by the time you realise the phenomena has hit your already 2 - 5 months into it and since the vaccine does not work for a month ... its actually a waste ? I agree if the climatic conditions occurred before the phenomena occurred ?

Also according to me option b is better as if there I an export ban I will give my cattle a pre-vaccine so
that my sales are not impacted

Outbreaks of Rift Valley fever occur irregularly in East Africa, several years apart. When outbreaks do occur, they kill thousands of cattle. A livestock vaccine against the disease exists but is rarely used. It is too expensive for farmers to use routinely, and since it is not effective until a month after vaccination, administering it after an outbreak begins helps very little. Nevertheless, experts predict that use of the vaccine will increase significantly within the next few years.

Which of the following, if true, provides the strongest justification for the experts' prediction?

(A) Rift Valley fever is spread by mosquitoes, but each outbreak is so widespread that it is impractical to control it by using insecticides.

(B) When an outbreak of Rift Valley fever occurs, unaffected countries often refuse to import livestock from the countries affected by the outbreak.

(C) It would take less than a month for producers of the vaccine to adjust their production operations to cope with a large increase in demand.

(D) Many cattle farmers in East Africa are nomadic or live in remote villages, and such farmers, who have little access to modern veterinary medicine, are particularly hard hit by outbreaks of Rift Valley fever.

(E) Recently published research has shown that certain identifiable climatic conditions are almost invariably followed, within two to five months, by an outbreak of Rift Valley fever.
gmat-admin's picture

We're told that a vaccine exists, but it's seldom used (for various reasons), yet the "experts predict that use of the vaccine will increase significantly within the next few years."

Why would vaccine use suddenly increase when farmers rarely used it in the past? What has changed?

For answer choice E, the keyword here is RECENTLY.

A RECENT discovery says that we can NOW predict when Rift Valley fever will hit us. In fact, we now have 2-5 months notice, which is enough time to vaccinate the cattle BEFORE the 1-month cut-off.

Answer choice B is invalid because it doesn't explain why the farmers are going to significantly increase their use of the vaccine in the next few years. That is, if unaffected countries have refused to import livestock IN THE PAST, why hasn't vaccine use already increased, and why will it suddenly increase?

Does that help?


Hi Brent thanks for the quick revert but my point for Option E is if the recent discovery is that certain climatic conditions follow the outbreak and not prior to the outbreak. if it was prior than maybe we can predict that the outbreak will follow and take precautions and the vaccine . But since the climatic condition's follow the outbreak we don't really have a time to react do we ? specially since the premise also mentions that the medicines take a month to react..... AM I missing something obvious or am I overthinking this ?
gmat-admin's picture

Aha! Now I see the issue :-)

Answer choice E says "Recently published research has shown that certain identifiable climatic conditions are almost invariably FOLLOWED, within two to five months, BY an outbreak of Rift Valley fever."

So, the climatic conditions come BEFORE the outbreak of Rift Valley fever, not the other way around.


I appreciated this video example. It's easy to mistake that one plant performs one way "here" and other similar plants will perform the same way in other states. After all, the link is not between plants and reproduction, but salinity and the polafish.
Very clear. Thanks for helping me understand.

Hi Brent, what difficulty level is this question?
gmat-admin's picture

It's pretty tricky. I'd say it's a 650-700 level question.

Office Hours

On December 20, 2023, Brent will stop offering office hours. 

Change Playback Speed

You have the option of watching the videos at various speeds (25% faster, 50% faster, etc). To change the playback speed, click the settings icon on the right side of the video status bar.

Have a question about this video?

Post your question in the Comment section below, and a GMAT expert will answer it as fast as humanly possible.

Free “Question of the Day” emails!