A couple should respect ______ parents,which is of primary importance to a family.
It was at 10 o’clock last night ________ the visitors finally arrived at Zunyi Airport.
Many websites have been _______ to help people study foreign languages.
As soon as he heard the news, a(an) of surprise appeared on his face.
I love animals and that’s the reason ______ I hate the people who kill wild animals for money.
Professor Li preferred _______ lectures to his students to _______ to meetings on scientific developments.