冬天穿保暖内衣可以帮助保持体温。

Wearing ___thermal underwear in winter helps retain body heat.

冬天跑步时我总会穿保暖内衣。

I always wear ___thermal underwear when running in winter.

滑翔机借助上升的暖气流在空中盘旋。

The glider circled in the ___thermal to stay airborne.