The chief reason for the population growth isn’t so much a rise in birth rates ________ a fall in death rates as a result of improvements in medical care.

The chief reason for the population growth isn’t so much a rise in birth rates ________ a fall in death rates as a result of improvements in medical care.

1. A.
   and
2. B.
   as
3. C.
   but
4. D.
   or

The chief reason for the population growth isn’t so much a rise in birth rates ________ a fall in death rates as a result of improvements in medical care.

     A. and                       B. as                            C. but                          D. or

（2010·湖南湘潭市外国语学校届高三第二次月考）25. The chief reason for the population growth isn’t so much a rise in birth rates ____a fall in death rates as a result of improvements in medical care.

A. and         B. as   C. but     D. or