因为S=πr2,
所以当圆的半径扩大4倍,面积扩大42=16倍.
故选:C.
China is a _____ country _____ to the third world.
A.developed; belongs
B.developing; belonging
C.developing; belonged
D.developed; belonged
在制品定额法适用于()。
A.大量生产
B.多品种成批生产
C.准时生产
D.单件小批量生产