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scientists didn't know much about lung cancer——.

来源:学生作业帮 编辑:作业帮 分类:英语作业 时间:2024/07/18 16:29:45
scientists didn't know much about lung cancer——.
A before long B until recently C long before D in the past few years
C long before 很久以前
A before long 不久后,肯定错了.
B until recently 直到最近,是和现在有关,不能用过去时didn't
D in the past few years 最近几年,理由同上.