We had a hard time ____________ the basketball match, but finally we made it. 

---Don't skate on the lake! ---Why not? Isn't it thick enough___________?

Would you like ________ ice cream now?

---Excuse me, how can I find useful information on the Internet?--- ________ the information you need, type in the keywords and then lots of websites will appear.

We know that she enjoys ______ books very much.