A.
B.
C.
D.
[单选题]A.2c㎡B.3c㎡C.4c㎡D.6c㎡E.A、B、C、D都不正确
[单选题]A.B.C.D.
[单选题]A.B.C.D.1E.
[单选题]A.增大B.减小C.不变D.条件不足,无法确定