中国大学MOOC: Sandbags will hold the flood waters ________ for a while.
中国大学MOOC: Sandbags will hold the flood waters ________ for a while.
Sandbags will hold the flood waters ________ for a while. A: back B: out C: up D: on
Sandbags will hold the flood waters ________ for a while. A: back B: out C: up D: on
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