Has is used when we are talking of something in the present . Had is used when we are talking of something in the past.
Examples:Today Joan has a book. (She now is in possession of a book)
Yesterday Joan had a book, (She was is in possession of a book a day ago)
Has and had are also a "helping verbs" which can be used with other verbs.
Examples:Joe has gone to the movies. (Joe is not here because he is [on his way or at] the movie theater)
Joe had gone to the movies. (In the past, Joe went to the movies and during this time something else happened which would be described in the following sentences.)
Yeah, that is fine.
You should use "are".
You should use did.
you should use meters
You should use your treadmill on a regular basis. You should use it every day if possible. You should use the treadmill for twenty to thirty minutes.
you should use you all
There are number of different kinds of gas you should use. The gas you should use depends on the situation.
Why should you improve your ability to use the library?
You should not. You should use centimetres.
you should use spagetti and sauce
when should you use written comunicatio
if we made mistake