The directions for operating this machine were so that we could not understand.
A. various
B. different
C. fundamental
D. plex
网友回答
A. various
B. different
C. fundamental
(答案→)D. plex
解析：various 各种各样的；different 不同的； fundamental 基本的； plex复杂的。
题意：操作机器的说明是如此的复杂以至于我们都不理解。所以D选项正确。