A:①②③④
B:③④⑥
C:②③④⑤
D:①③④⑥
What does the man want to buy?
__________ are his brothers.
____ ____ he often ____at Christmas?
抗原进入人体后,使人体产生一种抵抗该抗原的蛋白质是( )
读图,回答下列问题。