命题网络
参考答案：
任何两个命题，如果它们具有共同成分，则可以通过这种共同成分而使之彼此联系起来，许多彼此联系的命题组成了命题网络。
The factory produced a large amount of furniture last year, so far 65 percent of which _____ exported
to some European countries. [ ]
A. has been
B. are
C. was
D. were
在其他因素一定的条件下，边际贡献率与应收账款占用资金成反比。( )
