Jane’s mum was ill yesterday, so she had to look her.
A:at
B:for
C:after
D:out of
——The two old friends were ______ busy _____with each other ______ the time.——Yes. They haven't met for long.
读太阳系模式图,回答:
把汽油装在滴定管内,适当调节阀门,记录到汽油滴了400滴时,管内汽油少了0.4cm3,把其中一个油滴滴在水面上形成最大的油膜面积为3m2,试估算汽油分子的直径.
美国1787年宪法规定:立法权由国会掌握,行政权归于总统,司法权属于联邦最高法院。这一规定( )