Plant species differ in that renewed growth in spring can be triggered by day length or by temperature or else by a c...

hbrennan14@gmail.com on August 31, 2018

Can you please explain why it is C

Max-Youngquist on September 1, 2018

@lizD @hbrennan14@gmail.com the passage states that plant RG in spring can be triggered by DL, T, or both. So changes in when that trigger occurs year to year could be explained by DL, T or both. Since DL remains the same year to year, we know that the changes in when the trigger occurs year to year can't be fully explained by DL (otherwise the trigger would always occur at the same time). So T necessarily plays at least some role.

Looking at (C), we see a similar argument. We're told that some landfills charge by V, some by W and some by both. So differences in charges could be explained by V, W or both. Therefore, if there are different charges while holding V constant, then V can't fully explain the charges (otherwise they would be the same). So W must play at least some role.

I hope that helps!

BHR on March 24, 2021

I read C as if there were three distinct groups of landfill. the V, W, and the 'all others' and that they are exclusive in the charging structures. C then says 'at a particular landfill' without specifying which type of landfill it is (is it a V, W, or a both landfill?), and then applies the rule of both (V+W) to it. To me this differs from 'any plant species' as a single broad group that is effected by the 3 factors.

Victoria on May 2, 2021

Hi @BHR,

The similarity between the two is that there are three distinct groups: (1) affected by Factor X; (2) affected by Factor Y; and (3) affected by a combination of both Factors X and Y.

Both the stimulus and answer choice (C) conclude that, if similar things differ widely in Factor X, then they must be affected to some degree by Factor Y.

Stimulus

Plant species differ in that renewed growth can be triggered by day length (Factor X), by temperature (Factor Y), or else by a combination of both (Factors X and Y).

Therefore, any plant species whose growth is triggered on various days (Factor X) between years, then their growth must be affected to some degree by temperature (Factor Y). This means that they fall into the third group above i.e. they are affected by a combination of both factors.

Correct Answer

Landfills differ in that their charges are based on volume only (Factor X), weight only (Factor Y), or else by a combination of both (Factors X and Y).

Therefore, for any landfill which charges different amounts for loads of equal volume (Factor X), the charge must be affected to some degree by weight (Factor Y). This means that these landfills fall into the third group above i.e. they are affected by a combination of both factors.

Hope this helps clear things up a bit! Please let us know if you have any further questions.