It is uncertain side effect the medicine will bring about, although about two thousand patients have taken it.
I regret _________ going on a holiday to France because of the bad weather last week.
All __________ can be done has been done.
--- What do you think of the film Schindler’s List? --- This is the best film _______ I have ever seen.
I saw the beautiful garden _________ owner was an old man.
--- I’m so tired after a whole night work. --- ______ a rest?