—Hi, Bob! What's going on over there?
—Oh, Tom and Dick are playing chess, with a crowd of students watching them.
A:happening
B:appearing
C:working
商鞅变法成功的最根本原因是( )
在我国东北地区,人们对于马铃薯种植有着极为亲切的描述,“投下几粒马铃薯,多少都会有收成.只要开花,就能到田垄取‘蛋’糊口,解决温饱.”马铃薯的繁殖过程见如图的示意图,请回答下列问题.
下列属于不可遗传的变异是( )