if we take short breaks__.19. Food in small pieces could be eaten easily from the sun twigs which_ turned into chopsticks.20. Walls make of adobe take in the heat from the sun on hot days and give out that heat_ during cool nights， thus warning the house.21. …
结合时间状语“After a month at my senior high school”可知，事情已发生，谓语时态用一般过去时，get to know ，复数名词roommates 和hobbies 作宾语。
