问题
选择题
The professor explained this theory so clearly that this phenomenon was easy enough ________.
A．for us to work out
B．working out
C．for working out
D．to working out
答案
答案：A
句意：教授解释的这个理论如此的清楚，以至于这种现象对我们来说足够容易解决。 easy后常用to do 结构，所以选A。