从蝗虫的发育过程看,扑灭蝗虫的最佳时期应在( )
A:夏蝗
B:挖掘消灭受精卵
C:秋蝗
D:三龄前跳蝻
The mountain I visited last Sunday isn't very ___________. Few ___________ go sightseeing there.
—Excuse me, is this _______ bicycle?
—No, it isn't. _______ is over there under the tree.
如图所示是某同学用同一个物块做的一个探究实验,通过该实验可以得出的结论是____;该实验中盐水是配制的,只知密度比水大,根据该实验中弹簧秤的度数,可以求出盐水和____的密度,大小分别是____ 和____ .