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
答案是A
白勇的语法书里面明确提到these/this等不能作为句子主语，而且以前也有不少这样的错误例子（多为this不能作为主语），这里为什么these可以作为主语了，有些疑惑，虽然A是错的最少的一个选项。 | 
