简述小麦黄矮病的典型症状。
参考答案:
叶片的黄化和植株的矮化。叶片的黄化是从顶端开始象下延伸的,植株的矮化程度则因发病期及品种而异,发病越早,矮化越严重,病株一般不抽穗。
284. Unexpectedly, Maggie came out of the cage and ____ the letter from her and began to read aloud.
A.held
B.seized
C.snatched
D.Grasped
车辆在车间停放时,要采取()措施防止车辆移动。
A.拉紧驻车制动器
B.踩紧脚制动踏板
C.变速器操纵杆放在驻车挡或空挡
D.车轮下塞木块