The rabbit met the lion at a Christmas party
 

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Re: The rabbit met the lion at a Christmas party
 

1. Re your lion and rabbit - no problems with "become" as friendships do go on developing. You could limit though by saying soon rather than since then. The verbs are a bit weird, however, especially without clarifying time adverbials, especially to establish the reference point - ie the time of the action. I'd rewrite it as :

It was summertime, and the rabbit was thinking of his friend the lion. They had met at a Christmas party six years ago, and had become good friends since then.

orIt was summertime, and the rabbit was thinking of his friend the lion. They had met at a Christmas party six years ago, and had soon become good friends.

or, with this last one only :

It was summertime, and the rabbit was thinking of his friend the lion. They had met at a Christmas party six years ago, and soon became good friends.

The choice of the form of become depends on whether the writer chooses to see the reference point as still being summertime, as it was for the party (ie the events happen before that point and the perfect is used) or as the Christmas party (ie the event happened after that point and the simple past is used).

Re: The rabbit met the lion at a Christmas party
 

Re your second question concerning She has put the pudding in the fridge for three hours (it's much easier for other readers to find past questions and explanation if you start a new thread for each question and give it a specific title) :

No, it doesn't mean a repeated action, and the time phrase does not depend on the the verb. If it were repeated and if the time phrase did refer to the verb, it would be : She has been putting the cake in the oven for three hours. - clearly an unusual way to cook.
In this use of the present perfect ( ie past event(s) with a present result) there is a contrast in meaning between the simple and continuous. Compare :

Present perfect simple : I've cut my finger! = a single past event with a present result ( = my finger is bleeding)
Present perfect continuous : Someone has been cutting pictures out of this book! = continuous or repeated actions with a present result ( = the book is ruined)

So here the sentence is understood as : She put the cake in the oven and it's cooking at the moment. It must cook for three hours.
She has put the cake in the oven = single past action with present result (= and it's cooking at the moment) with the meaning of the time phrase being inferred to refer to the length of time of the cooking - not of the action of putting it in the oven.

This is a good example of why, although the present perfect verb form includes reference to a past event, it is actually a present tense - the focus is on what is happening at the moment - even if that is not explicitly stated in the sentence - and the past event is only the incidental cause of the present situation.

See this thread for an analysis of the present perfect simple and continuous : http://www.eslhq.com/forums/esl-foru...ng-done-37301/

Re: The rabbit met the lion at a Christmas party
 

Thank you for your clear answer. But I must read it and re-read it.

Re: The rabbit met the lion at a Christmas party
 

Yes.