(2013·山东卷)There is no simple answer，________is often the case in science.

Must I finish the exercise at school? — No, you don’t have to. You doit at home.

____________ jumped into the freezing river to rescuethe drowning girl deserved to be praised.

Excuse me, could you tell me ________

Is there island in Wenzhou —Yes, it’s Dongtou Island.