After studying in a medical college for five years,Jane________her job as a doctor in the countryside.
A:set out
B:took over
C:took up
D:set up
“春蚕到死丝方尽”,家蚕吐丝结茧后,在蚕茧中所处的时期是( )
下列各式中,变形正确的是( )
关于东北平原成为商品粮基地主要原因的叙述,不正确的是( )
下图为四幅区域示意图,按比例尺从小到大顺序排列正确的是( )