you'd better___(keep)the fire burning in the eveningshe opened the door ___(let)the children come

you'd better___(keep)the fire burning in the eveningshe opened the door ___(let)the children come
you'd better___(keep)the fire burning in the evening
she opened the door ___(let)the children come

you'd better___(keep)the fire burning in the eveningshe opened the door ___(let)the children come
1.keep
you'd better do sth 表示建议“你最好做某事”,do为动词原形
2.to let
不定式to接动词原形,表示目的"目的是"

you'd better_keep__(keep)the fire burning in the evening
she opened the door _to let__(let)the children come

应该填写：

keep had better后跟动词原形
to let
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