看图写单词。
_________ __________ ___________ __________
book, pen, school, marker
In the face of difficulties and drawbacks, we should learn to comfort ourselves and _______our high spirits all the time.
A.keep up
B.go up
C.pick up
D.hold up
下列有关孟德尔选用豌豆作为试验材料的原因中,不正确的是()
A.豌豆是异花传粉植物
B.豌豆是闭花受粉植物
C.豌豆有利于进行人工杂交试验
D.豌豆的一些品种之间有易于区分的性状