how to justify that past tense is more suitable here?

[Awence]

A question like this appeared in my test paper.

When____________Britney Spears in concert?

- The answer provided is "did you see".

And i m seeking for a proper explanation to justify why "have you seen" is not a suitable answer here because i can anticipate that my students would throw me the questions like that.


On the other hand, i also need another justification for the situation below:

Lucy is now 20 years old and she has just started a three-year degree course at university. While she was growing up she often felt homesick because she missed her friends but now she loves her life.

Her parents, however, [/b]are thinking of moving back to england. They had been saving up to buy a bungalow in Cornwall for several years. They want to go back soon!

The words in bold are the answers as provided by my text book. HOw could i justify the use of the present continuous tense. And can other tenses like present perfect continuous be an alternative answer.

Thanks in advanced for someone who is willing to lend a helping hand.

[Micawber]

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Hello Awence.

1-- Unfortunately, present perfect is also possible in the Britney Spears question-- as is future: 'When are you going to see BS in concert? and probably a few other verb forms as well. Without context, it is impossible to choose.

2-- Present continuous here is used in its usual way: to indicate present activity. They are thinking now. Present perfect (they have been thinking of moving back) puts a slightly different slant on the activity: the thought process started in the past and is continuing now.

Does that help?
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