The traffic problems have severely affected economic development. ________, we must spare no efforts to solve them.

There is no doubt that I'm trying to do what is best, but ________ I have got to consider the cost.

 The melon the Smiths served at dinner would have tasted __________ if it had been put in the fridge for a little while. 

She didn’t mention her troubles to Mr. Li，who might have helped her ______.

I can ______ be a teacher. I’m not a very patient person.