A.
B.
C.
D.
[单选题]A.B.C.D.
[单选题]A.2f′(a)B.f′(a)C.f′(2a)D.0
[单选题]A.充分但不必要条件B.必要但非充分条件C.充分必要条件D.既非充分也非必要条件
[单选题]A.4πB.3/4πC.2πD.4π/3
[单选题]A.-2xdxB.C.D.