题目如下：After the public announcement of the merger of two firms an investor makes abnormal returns
by going long on the target firm and short on the acquiring firm. This most likely violates which form
of market efficiency?

A. Semi-strong form only
B. Weak and semi-strong forms
C. Semi-strong and strong forms

官方给的答案是B，我有点想不通，希望大家交流下或者高人指点下。

violation for semi-strong form是很明显的，官方的解释是Note that the semi-strong form of market efficiency encompasses the weak form. Therefore, both weak and semi-strong forms of market efficiency are violated. 可是strong form才是semi-strong的升级版啊，那么违反prices adjust quickly to new public information应该是同时违反semi-strong和strong才对啊。

总觉得答案是错的，求解释！！多谢