aflaam wrote:Besides adding complementary flavors to many foods, hot sauces stimulate the release of endorphins in the brain, just as exercise does, and these have a pain-relieving effect like morphine's.
(A) hot sauces stimulate the release of endorphins in the brain, just as exercise does, and these have a pain-relieving effect like morphine's
(B) hot sauces stimulate the release of endorphins in the brain, like exercise, and they have a pain-relieving effect that is like morphine
(C) hot sauces and exercise both stimulate the release of endorphins in the brain, and they have a pain-relieving effect like morphine
(D) the release of endorphins in the brain is stimulated both by hot sauces and exercise, and they have a pain-relieving effect like morphine's
(E) the release of endorphins in the brain is stimulated by hot sauces, just as with exercise, and these have a pain-relieving effect like that of morphine
Source GMAT prep
OA A

Is B also incorrect because sauce is compared with exercise apart from the faulty comparison in second part?

This correctly uses the subject "hot sauces" after the modifier "adding flavor." "Just as exercise does" is comparing to the act of releasing endorphins - this is a logical comparison. "These" refers to "endorphins," whose pain-relieving effects are correctly compared to morphine's pain-relieving effects.

I assume you mean the possessive "morphine's"?

In COMPARISONS, we have to compare apples to apples. There are often several correct ways to express a given comparison:

Correct:
My puppy is well-trained, unlike that of my sister.
My puppy is well-trained, unlike my sister's.

Incorrect:
My puppy is well-trained, unlike my sister. (Unless she herself is not well-trained!)
I trained my puppy well, as did my sister. (Implies that she also trained my puppy, rather than her own)

The GMAT often prefers to use "that of" or "those of" in correct answers, but the possessive is also perfectly correct. But note: because "that" or "those" have to agree in number with the noun they replace, we cannot use them if we're comparing singular to plural or vice versa.
For example, if I had one puppy but my sister had two, I could NOT say:
My puppy is well-trained, unlike those of my sister.
In this case, I would have to use the possessive (or rearrange the sentence some other way).

In this GMAT problem, "the pain relieving effect of endorphins" and "the pain relieving effect of morphine" are both singular, so either of the following would have been correct:
... these [endorphins] have a pain-relieving effect like morphine's.
... these [endorphins] have a pain-relieving effect like that of morphine.