1. My father went to college in the age of 45.(x)
My father went to college at the age of 45.(√)
in an / the age of.二是指“在……的时代”，如:We are living in the age of technology.(我们正生活在一个科技时代。)指“在几岁时”，须用at the age of+数字。
2. How old did you start smoking? (x)
At what age did you start smoking?(√)
how old是形容词词组，只能搭配be动词来用，如:How old are you / is he?(你他多大年纪?)at what age是副词词组，可以修饰动词。
3. When I was at your age, I used to like jazz a lot.(x)
When I was your age, I used to like jazz a lot.(√)
at your / his / her age是副词词组，不能作be动词的表语，如:At his age he can be very rebellious.(在他这个年龄可能是很叛逆的。)be sb's age表“在某人的年纪时”。
4. People like my age tend to become more conservative.(x)
People of my age tend to become more conservative.(√)
people like my/your/his age没有意义，因为people和age没法“像”。people / boys /girls of your / my / his age是正确的用法，这里的of表“属于”，即“属于……的年龄”之意。另有be of an age+不定式，也有“属于”之意，如:The boy is of an age to know better.〔按年龄这个孩子应该懂事了。)
5. I have two children, aging 12 and 15.(x)
I have two children, aged 12 and 15.(√)
aged+数字，表“年龄为……”。aging可当名词或形容词，意为“老化”或“老化的”，如:The aging process comes slowly but surely.(老化的过程来得很慢但绝错不了。)
6. These toys are designed to target children aged 7 and 10.(x)
These toys are designed to target children aged between 7 and 10.(√)
These toys are designed to target children aged 7 to 10.(√)
children aged 7 and 10是指“7岁和10岁的儿童(即不包括8岁、9岁的儿童)”，显然不合理;aged between A and B=aged A to B，是指“介于A和B的年龄层”。
7. Jane is applying for a job at a real estate agent.(x)
Jane is applying for a job at a real estate agent's / agency.(√)
agent指的是“经纪人，从业人员”，如:a travel agent就是指“一名旅游从业人员”。agent's或agency指的是“公司或机构”，如:a news agency就是指“一家报社”。
8. The war had ended well over 50 years ago.(x)
The war ended well over 50 years ago.(√)
ago=before now，是以现在(说话时)为基准的一段时间以前，与一般过去时搭配使用。
9. Have we met ago?(x)
Have we met before? (√)
ago不能单独使用，其前须有明确的一段时间，如:a week/two days ago。before有两种用法:(1)笼统的以前(可搭配现在完成时或一般过去时)，如:I (have) never heard of the man before.(我之前从未听说过这个人。)(2)某个过去时间的以前(常搭配过去完成时).如:The patient had died two hours before the doctor came.(医生来时，病人已经死亡两个小时了。)
10. My father did not agree with my brother studying abroad.(x)
My father did not agree to my brother studying abroad. (√)
agree with sb/sth是指“同意某人的看法或意见”，如:My father does not agree with my mother about everything(爸爸和妈妈对事情的看法从不相同。)agree to则是“同意(某人的)建议或做法”，有“赞成”或“准许”之意。