He always has a lot of _______ ideas in his mind , and sometimes we do not even know what he is thinding about.

When traveling alone in the mountains, you ’d better take a _______ with you in case you get lost.

When a spacecraft travels, one of the major problems is reentry into the Earth ’s _______.

Thisriverformsanatural_______betweenChinaandKorea.

The engineers in this lab spent several weeks _______their plans for the new bicycle.