Jack almost fell off a big tree while climbing it, but managed to __________until help came.

This book isn’t mine. ________can it be?

Books are made __________ paper while paperis mainly made __________ wood.

I like the dumplings made ________ my mother best.

The electronic red-packet has been so ______ that AliPay and Tencent Wechat compete against each other openly and secretly since the beginning of this year.