【单选题】They did researc h on how __________ their customers.
【判断题】若 , 在点 处都不可导,则 点 处也一定不可导
【判断题】临时轴是在创建圆柱和圆锥体是隐含生成的。 ( )
【单选题】Marconi moved to England because ______.
A.
he did not get financial support for his research in Italy
C.
his research had to be conducted in England
D.
his research fellow was in England