A:(a﹣1)2=a2﹣1
B:(2a)2=2a2
C:a2•a3=a6
D:a•a2=a3
Toby is ________. He cries. ( )
①作BE∥AD交DC于E .②连接AC,作BF∥AC交DC的延长线于 F .③作AG⊥DC于G .
----Miss Lin _____ my desk-mate with her lessons when I left school.
----She is really a nice teacher.