50. He was [so] excited after hearing the news [and] he [could not] fall asleep
        A                          B                  C     
 [immediately].             
       D
答案：B应改that，固定结构：so…that…如此…以至于。

51. You [will not able] to pass the examination [unless] you work [harder] than
           A                            B             C
you [do] now. 
     D
答案：A短语搭配，应改will not be able to能够做某事。

52. Only when [it started] to rain [he noticed] that he [had left] his raincoat
               A              B              C
 [somewhere].
       D
答案：B应改为did he notice因为Only放在句首，句子要到装。

53. The waste, [according] to the people there, has [already] found [their] way
              A                     B              C  
into [the] drinking water.
          D
答案：C应改为its,代指前面的waste，为不可数名词。

54. If you [try to] learn [too] many things [at a time] you may get [confusing].
       A      B                  C                   D
答案：D应改为confused。主语是you指人，动词的现在分词作形容词时，不能修饰人，只有过去分词才可以修饰人。

55. [After] his [graduation] [from] the university, he has [worked] in a famous 
    A            B      C                     D
computer company.