This is _____ pen and ________ is in the pencil-case.

When did you _________ the Chinese YoungPioneers

That book I lent to you yesterday is than this one.—Really I’ll return it to you as soon as I finish reading it.

Her sister ______ a rich man. They ______ for twenty years.

Under no circumstances _______ the difficulties when they were on an expedition to the Antarctic．