A.
B.
C.
D.
[单选题]A.a=-4,b=1B.a=4,b=-7C.a=0,b=-3D.a=b=1
[单选题]A.B.C.D.
[多选题]A.B.C.D.E.
[单选题]A.立即停止戴用B.还应戴用1周C.还应戴用1个月D.还应戴用3个月E.还应戴用6个月或更长