1) If I am here I will help you.
If I was here I would help you.
If I had been here, I would have helped you.
2) If it is possible we will begin this work at once.
If it was possible we would begin this work at once.
If it had been possible, we would have begun this work at once.
3) If she has all the necessary books she will make her report in time.
If she had all the necessary books she would make her report in time.
If she had had all the necessary books, she would have made her report in time.
But he does not like lemonade.
As
before
when
then
seconds later
a few hours later
<span>do you have a computer</span>