HSK 7-9
扩散
kuòsàn动
to spread; to proliferate; to diffuse
烟雾很快向四周扩散开来。
Yānwù hěnkuài xiàng sìzhōu kuòsàn kāilái.
The smoke quickly spread in all directions.
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Appears across levels (7-9) in the HSK 3.0 word list.