开垦土地
参考答案:
是指以垦殖为目的开发土地,即开垦荒地为耕地用于农作物的种植。
—I’m considering to Qingdao by air for my holiday.
—Why not try by ship for a change?
A.going;to travel
B.to go;to travel
C.going;travelling
D.to go;travelling
在干燥洁净的空气中,体积分数约为21%的是
A.氧气
B.氮气
C.二氧化碳
D.稀有气体