Question

1.I don't know the meaning of the word. That's why I have to look it up

-> If

2.Since it is foggy, the plane can't take off

-> If

3.The shoes are so big that I can't wear them

-> If

4.The floor is so dirty that we clean it many times

-> If

5.I can't send her a postcard because I don't know her address

-> If

Answer 1

1.I don't know the meaning of the word. That's why I have to look it up

-> If I knew the meaning of the word.,  I would not have to look it up

2.Since it is foggy, the plane can't take off

-> If it was not foggy, the plane could take off

3.The shoes are so big that I can't wear them

-> If the shoes were small, I could wear them

4.The floor is so dirty that we clean it many times

-> If the floor was not dirty, we would not clean it many times

5.I can't send her a postcard because I don't know her address

-> If I knew her address, I could send her a postcard