Alice’s kids are well-behaved, but ______ of her brother are impolite.

Some people thought ________ possible to live on out space in the future .

 — How many students are going to the Great Wall? — ____.

--Do you know any Russian? –Yes, but ___.

I would like to buy some good English reference books, but _______ was available from the bookstore, where I only found some Chinese ones.