He knew nothing about it _____ I told him.[ ]
A. since
B. because
C. until
D. after
答案:C
Today, people are paying more and more attention to their health, books on keeping healthy extremely hot.
A.to make
B.making
C.make
D.made
在标准大气条件下,场压高度等于:().
A.标准气压高度
B.海压高度
C.绝对高度
D.相对高度