prep-134，有关对称问题，麻烦牛牛赐教！

800120summer

Among lower-paid workers, union members are less likely than nonunion members to be enrolled in lower-end insurance plans imposing stricter limits on medical services and requiring doctors to see more patients, and spend less time with each.
A.imposing stricter limits on medical services and requiring doctors to see more patients, and spend
B.imposing stricter limits on medical services, requiring doctors to see more patients, and spending
C.that impose stricter limits on medical services, require doctors to see more patients, and spend
D.that impose stricter limits on medical services and require doctors to see more patients, spending
E.that impose stricter limits on medical services, requiring doctors to see more patients and spending
答案选D， 请问牛牛们A怎么不可以，是不是A里spend要和seed对称是不是一定要加to
还有一个知识点的请教，就是两个句子间连接可以加逗号，那么两个短语间连接能不能加逗号，就像本句中的require doctors to see more patients, and to spend less time with each, 这里的逗号能这么用么？！
万分感谢！

abby666666

不一定加to
这里A会有歧义：are or to see