解题思路:
∵
A
B
//
C
C
′
,
∠
C
AB
=
70
0
,
∴
∠
AC
C
′
=
∠
C
AB
=
70
0
.
∵
△
A
B
′
C
′
由
△
ABC
绕点
A
旋转得到,
∴
△
ABC
≌
△
A
B
′
C
′
.
∴
A
C
=
A
C
′
.
∴
∠
AC
C
′
=
∠
A
C
′
C
=
"
70
∘
"
∴
∠
C
A
C
′
=
180
−
∠
AC
C
′
−
∠
A
C
′
C
=
"
40
∘
.
"
∴
∠
BA
B
′
=
40
∘
.
故选C.
C.