若函数f(x)的反函数是f-1(x)=2x+1,则f(1)的值为( ).
A.-4
B.4
C.-1
D.1
由f-1(x)=1得
2x+1=1,
∴x=-1,
∴f(1)=-1.
故选C.
脑干最常见的肿瘤是()
A.室管膜瘤
B.星形细胞瘤
C.海绵状血管瘤
D.血管母细胞瘤
E.转移癌
This book _______ her 10 yuan, but I only ________ 5 yuan on the same one.
A.spends; spend
B.spends; cost
C.costs; cost
D.costs; spend