机体获得人工主动免疫的方式是（）
A.注射抗体
B.注射类毒素
C.注射抗毒素
D.注射胎盘球蛋白
E.折射丙种球蛋白
参考答案：B
He sat back on the chair, listening to the MP4 and ____ . [ ]
A. looking at ease
B. looked at ease
C. being looked at ease
D. to look at ease
The two sides ____a series of compromise suggestions and then signed the contract.
A．made out
B．worked out
C．put out
D．picked out
