研究“100毫升水能溶解多少克食盐”中,需要准备的仪器是____。
1929~1933年,席卷整个资本主义世界的经济危机爆发于( )
如图为根尖结构模式图,据图回答问题:
— I haven't ________ Mike for a long time.
—I think maybe he is too busy to write to you.