stormier wrote:Cold blooded animals, such as snakes, lizards, and salamanders, have developed a variety of mechanisms which keep body temperatures at a comfortable level.

A. which keep
B. to keep
C. that keep
D. which kept
E. in order to keep

Really, the only valid choices are A and C; remember that "that" is restrictive (what follows is key information narrowing down the noun before) and will not have a comma, and "which" is usually not restrictive and will have a comma. Lacking a comma in the non-underlined portion, you're best off choosing C.

Really, the only valid choices are A and C; remember that "that" is restrictive (what follows is key information narrowing down the noun before) and will not have a comma, and "which" is usually not restrictive and will have a comma. Lacking a comma in the non-underlined portion, you're best off choosing C.

This is a question from McGraw Hill's verbal practice workbook. I had made the same choice.

A and D are clearly losers.

Why have you discarded B and E ?

My reason to discard B and E was a change in the meaning of sentence. Both B and E make the sentence sound as though the animals deliberately developed those mechanisms - but now, I am not sure whether my reasoning is correct, or is a "sounds good to the ear".

According to OA, C is incorrect, because ....a variety of mechanisms.... is singular and should be followed by that keeps

stormier wrote:

Really, the only valid choices are A and C; remember that "that" is restrictive (what follows is key information narrowing down the noun before) and will not have a comma, and "which" is usually not restrictive and will have a comma. Lacking a comma in the non-underlined portion, you're best off choosing C.

This is a question from McGraw Hill's verbal practice workbook. I had made the same choice.

A and D are clearly losers.

Why have you discarded B and E ?

My reason to discard B and E was a change in the meaning of sentence. Both B and E make the sentence sound as though the animals deliberately developed those mechanisms - but now, I am not sure whether my reasoning is correct, or is a "sounds good to the ear".

According to OA, C is incorrect, because ....a variety of mechanisms.... is singular and should be followed by that keeps

The intention of the sentence is to convey that Cold blooded animals have developed XYZ(mechanisms)..
XYZ keep body temp at comfortable level ....stress is on what XYZ does

what B and E convey is that Cold blooded animals have developed XYZ(mechanisms) ..
XYZ have been developed to achieve something(comfotable level)..stress is on why XYZ adopted

HTH!