Look ____ Ray. He is ____ the tree. [ ]
A. on; for
B. for; at
C. at; in
C
Bob, you can't go out to play with your friends until your homework
A．will finish
B．is finished
C．will be finished
D．has finished
下列排斥反应，哪个是由于受者体内存在针对供者特异性抗原的预存抗体引起的（）。
A.超急性排斥反应
B.加速性排斥反应
C.急性排斥反应
D.慢性排斥反应
E.以上都不是
