Question

complete the following sentence which one word correct I saw two movies last night ......... ​

Answer 1

Well, one should always use ‘watch’ when it comes to movies (not ‘see’).

For your question

I have seen this movie is an example of Present Perfect tense.

When we use present perfect tense we are referring to actions which started in the past and are still happening or those actions which are finished but have an impact on the present.

For e.g. I have lost my keys. (Implies I do not have a key now so I cannot get into my house)

I saw this movie is Simple Past tense.

When we use simple past we refer to finished actions and those actions, results of which do not have an impact on the present.

There is a finished time word associated with simple past.

For e.g. I lost my keys yesterday. (Implies I lost them but now I have bought new ones or probably have found them).

Now as for your question you should say I watched this movie yesterday or any other time because yesterday refers to a finite word hence simple past.

Otherwise you should say I have watched this movie. (Implying you have no intentions of watching it today.