氯瓶装有2个针阀,使用时2个针阀应()放置
A.上下
B.左右
C.45度斜着
D.无要求
参考答案:A
______ have been made for nearly three decades to increase the amount of precipitation from clouds by seeding them with salt or silver iodide.
A.Devices
B.Hypotheses
C.Attempts
D.Commissions
稀浆封层一般用于()及以下公路的预防性养护,也适用于新建公路的下封层。
A、一级
B、二级
C、三级