A.对
B.错
[判断题]A.对B.错
[单选题]A.不变B.扩大2倍C.扩大4倍D.缩小一半E.缩小为原来的1/4
[单选题]A.a任意,b=0B.a任意,b=-1C.D.
[单选题]A.B.C.D.