European football is played in 80 countries, （）it the most popular sport in the world.

单项选择题—I wonder why Mr. Green looks quiet in class. —I'm not sure, but he （）a small accident driving here.

A. could have
B. might have
C. might have had
D. must have had

单项选择题I have been keeping the portrait．I can see it every day （）as it always reminds me of my childhood in Paris．

A．since
B．where
C．as
D．if

单项选择题终身教育思想形成于20世纪60年代的欧洲，由( )首先提出。

单项选择题美国的实用教育家杜威的代表作是( )。

单项选择题我国第一个正式实施的学制是( )。