Among lower-paid workers, union members are less likely than

D for me.

lower-end insurance plans do 2 things:
1)impose stricter limits on medical services
2)require doctors to see more patients

the 2) above makes doctors spend less time with patients.
It is not lower-end insurance plans that spend less time with patients.

A is wrong because the use of 'spend' is incorrect. (as if plans spend less time)

B is wrong for the same reason, though it looks parallel it means all three actions are done by insurance plans.

C is same as B just that it uses base form of verb instead of ing form

D correctly indicates that 1) & 2) above are done by insurance plans and spending less time is outcome of 2)

E indicates that only 1) is done by insurance plans and remaning are outcome of 1)