式子“a+ba”可以改写成请选择ABC9_+U,o+m1k+g4b3I5`1e6f'G,@6B;F2Z
A.（a+b）b5`1e6f'G,@6B;F2Z
B. a（a+b）5`1e6f'G,@6B;F2Z
C. a（1+b）5`1e6f'G,@6B;F2Z