-- What Peter now?
-- He is reading in his room.
A:does; do
B:are; doing
C:is; doing
请把下面的诗文名句补充完整。①假如生活欺骗了你, , !忧郁的日子里需要镇静。② ,关山度若飞。 ,寒光照铁衣。《木兰诗》③峨眉山月半轮秋, 。(《峨眉山月歌》)④ ,散入春风满洛城。(《春夜洛城闻笛》)
如图说明狗“铃声﹣唾液分泌”反射的建立过程,据图回答: