50.I only wish he showed half as much for his English lessons.

四级词汇讲解:

wish在表示愿望时，使用的频率很高。可以用在陈述句或者感叹句中，表示与事实相反的情况，或表示将来不太可能实现的愿望，因此从句中必须用虚拟语气。如:

※ He wished he hadn't said that.他希望他没讲那样的话。

※ How I wish I were as tall as you are.我真希望和你一样高。

本中的half as much其实是倍数的表达法half as much as he showed(比较结构halfi/a quarter/twice/three times+as…as)的缩略表达。如:
I won't marry a man who is twice as old as me.我不会嫁给一个岁数比我大一倍的人。