We should do what we have to do________ we can do whatwe want to do in the future.

The plant is dead. I ______ it more water.

I hope you can ____ and see us next timeyou come to Shanghai. — Sure, I will.

（题文）(2015·北京)___________the early flight, we ordered a taxi in advance and got up very early.

These two kinds of ways are totally different in nature, and we should not _______ the two.