They still go on working, ________ they feel tired.

Which do you like ________，tea，orange or water?

 - It's raining heavily outside.- _______, I will go back home because my son has been left alone at home.

— Have you ________ watched the dolphin show in the Ocean Park in Hong Kong?—Not _________.

The article is ________ more difficult than that one, so I think I can understand it with the help of a dictionary.