胸腺是哺乳动物发生最早的免疫器官。()
参考答案:对
腹主动脉瘤的分类:( )、( )、( )。
I don’t know when my father ______back , but I’ll tell you when he ______back.
A.comes; comes;
B.come;come
C.come; will come
D.will come; comes