Ecologist: One theory attributes the ability of sea butterflies

Can someone explain how D is the answer?

There is some compound being produced by butterflies. And, that compound is tested by putting on each pellet. What is the difference between an individual compound and combined compound?

Sent from my Redmi Note 3 using GMAT Club Forum mobile app

yes C is a tempting trap
I go with D as it directly shows the flaw in the conclusion assumed by splitting the compounds and experimenting whereas C deals with the assumption part of the theory 'while another attributes this ability to various chemical compounds they produce'

Can you explain what the option C means?
Thanks!

Test was done with the individual chemical compounds.We do not know what would happen if multiple compounds were mixed together. D states the same.Hence the answer.

C is out of scope, as the conclusion is not based on the condition sufficient / required for predators to behave certain way.

treats a condition sufficient for sea butterflies’ ability to avoid predators as a condition required for this ability
Treats condition sufficient as condition required

Example1: P-->Q; P maybe sufficient to result in Q .but P may not be a required condition
Example2: Red+ Blue --> Purple; Red is a required color to make a purple but red is not sufficient

Ability to various chemical compounds maybe be sufficient but it may not be required
ability to various colors or many other factors ---> avoid predators
ability of various color is just one of many factors that can avoid predator.


But for this argument, flaw is that ecologist thinks if something is applicable for A, it may also be applicable for B. Hence D is correct; not C.

Ecologist: One theory attributes the ability of sea butterflies to avoid predation to their appearance, while another attributes this ability to various chemical compounds they produce. Recently we added each of the compounds to food pellets, one compound per pellet. Predators ate the pellets no matter which one of the compounds was present. Thus the compounds the sea butterflies produce are not responsible for their ability to avoid predation.

The reasoning in the ecologist’s argument is flawed in that the argument


(A) presumes, without providing justification, that the two theories are incompatible with each other X
-justification was certainly provided

(B) draws a conclusion about a cause on the basis of nothing more than a statistical correlation X
-nothing about correlation exists in the passage

(C) treats a condition sufficient for sea butterflies’ ability to avoid predators as a condition required for this ability X
-the author does not treat any condition as 'required'

(D) infers, from the claim that no individual member of a set has a certain effect, that the set as a whole does not have that effect
CORRECT. The author inferred on the basis of a select few predators, that all of the predators would not avoid the pellets.

(E) draws a conclusion that merely restates material present in one or more of its premises X
-the author didn't do this.