1. Children of this age are easy to make mistakes.(x)
Children of this age are apt to make mistakes. (√)
easy表“容易的”，针对事物而不针对人，如:These questions are easy to answer.(这些问题很容易回答。)be apt to = tend to=be inclined to,表“有……之倾向”的意思。
2. Many industries have moved into the electronic area.(x)
Many industries have moved into the electronic arena.(√)
area是有关“地区”最笼统的一个词。arena本意为“竞技场”，引申为任何“角逐的领域”，如:enter the political arena即“进入政界”的意思。
3. A new difficulty happened when we tried to solve the problem.(x)
A new difficu勺arose when we tried to solve the problem.(√)
happen / occur / take place是指事件的“发生”。difficulty / problem / issue / question的“发生/产生”只能用arise.
4. Arithmetics is a branch of mathematics. (x)
Arithmetic is a branch of mathematics. (√)
arithmetic不可加s, mathematics恒有s，为固定用法。
5. Susan wouldn't stop crying until her boyfriend took her under his arm. (x)
Susan wouldn't stop crying until her boyfriend took her in his arms. (√)
take / hold sb in one's arms即“将某人紧紧抱在怀里”，为固定用法。under one's arm 是指“把某物挟在腋下”，如:Helen was carrying a book under her arm.(海伦将一本书挟在腋下。)
6. Keep that guy at an arm's length.(x)
Keep that guy at arm's length. (√)
keep sb at arm's、length意为“跟某人保持适当距离”，为固定用法，不可在arm's之前加an。但cost sb an arm and a leg这个词组须加an，如:It will cost an arm and a leg to buy a house like this(要买一栋像这样的房子是需要花很多钱的。)
7. Rachel's strange look arose our suspicions. (x)
Rachel's strange look aroused our suspicions.(√)
arose是arise的过去式，为不及物动词，其后不可直接接宾语，但arise from(起源于)可接宾语，如:Our misunderstandings arise from the lack of communication.(我们之间的误会是由缺乏沟通引起的.) arouse one's sympathy / suspicious/curiosity 表.“引起某人的同情/怀疑/好奇”.为固定用法。
8. At his arrival in Taipei,he went straight to the Grand Hotel. (x)
On his arrival in Taipei, he went straight to the Grand Hotel.(√)
on / upon sb's arrival 表“某人一抵达(某地)”，为固定用法。
9. Early arrival may get the best seats. (x)
Early arrivals may get the best seats. (√)
arrival 表“抵达”时，通常是不可数名词:作“抵达的人或物”解时，是可数名词。
10. Do you like modem arts? (x)
Do you like modem art? (√)
If you don't like the sciences, you may pick up the art. (x)
If you don't like the sciences, you may pick up the arts. (√)
art表“艺术”时，是抽象名词，不可数，如:Renaissance art(文艺复兴时期的艺术); 作“人文学科”时.是可数名词，且用复数。