The demand for _____ skilled workers is still increasing.

David apologized to me yesterday. __, I won't forgive him for it was not the first time that he had hurt me.

It’s widely known that first aid is      important and you can save lives if the right action is taken.

A good book is like a good friend. You cannot keep it          long.

＿to my regret, I am unable to accept your warm invitation.