农田氮素控制的途径?
参考答案:
(1)改进氮肥施用技术分次施肥、氮肥深施、缓效肥等
(2)平衡施肥和测土施肥
(3)采用硝化抑制剂
(4)合理灌溉
(5)做好水土保持工作
如图所示为精确度为0.1mm的游标卡尺测量一物体的长度后用定位螺丝将游标固定后情况.则该物体的长度为______mm.
Many parents feel worried about whether the kids will adjust to _____ from them. [ ]
A. being away
B. be away
C. having been away
D. had been away