问题描述：
请问为什么用covering ：seen from the moon,our earth ,with water covering
_______ from the moon,our earth with water ______ twenty percent of its surface,appears as a blue ball.
a.Seen,covered b.Seen,covering
.第一空我懂 ,想知道cover为什么用ing ,不是被水覆盖的吗?
_______ from the moon,our earth with water ______ twenty percent of its surface,appears as a blue ball.
a.Seen,covered b.Seen,covering
.第一空我懂 ,想知道cover为什么用ing ,不是被水覆盖的吗?
问题解答：
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