①淞沪会战
②太原会战
③徐州会战
④枣宜会战
A:①②③④
B:①②③
C:①②
D:②③④
Studying in groups is necessary __________ you want to do well in school.
将某抗原先后两次注射到同一个小鼠体内,其体内抗体水平的变化如下图所示。下列叙述中不正确的是( )