He has ________ in touch with his foreign friends for many years.
A:kept
B:had
C:keep
D:have
高速公路的隧道和桥梁最多.如图是一个隧道的横截面,若它的形状是以O为圆心的圆的一部分,路面AB=10米,净高CD=7米,则此圆的半径OA=
( )
选择每组单词都含有的音标填空
( ei;aɪ;ɔi;au;əu)