—Robert is indeed a wise man.—Oh, yes. How often I have regretted ______ his advice!
At home, he keeps some pets,to which he ______ all his spare time.
----Go for a picnic this weekend, OK? ----_____________. I love getting close to nature.
The couple went through all their pockets _________ their passports.
Some pre-school children go to a day care center, ________ they learn simple games and songs.
The waste can be recycled into new products, which _________ will save natural resources.