Mr Li is one of the businessmen who _____ very rich. [ ]
A. is
B. are
C. was
D. were
答案:B
图中①与②两大洲之间的分界线是:
A.土耳其海峡
B.白令海峡
C.乌拉尔山脉
D.苏伊士运河
在双缝干涉实验中,光的波长600nm,双缝间距2mm,双缝与屏的的间距为300cm,则屏上形成的干涉图样的相邻条纹间距为()mm。
A.0.45
B.0.9
C.9
D.4.5