题干
28. --- Is Bob still performing?
--- I’m afraid not. He is said _____ the stage already as he has become an official.
A：to have left
B：to leave
C：to have been left
D：to be left
答案(点此获取答案解析）
A
H+ + In-（黄色）△H＞0对上述平衡解释不正确的是