Is ____ dangerous to swim in the river alone?
Don’t you think the world would be an easier place to live in, if we all ________ the same language?
Knowing ________ you’re good at and doing even more of it creates excellence.
It is a wise father ________ knows his child.
—May I smoke here? —Choose a seat in the smoking section, if you ________.
---Would you like to go out for a walk? ----.