A:正数
B:负数
C:都不算
猜猜下面说的是哪种小动物。
Its ears are long. Its eyes are small. Its mouth is small. Its tail is short. What is it?
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如图所示,一物体置于水平面上同时受到水平拉力F1和F2的作用,已知F1=4N和F2=10N,物体静止不动.现撤去F2,则下列说法正确的是( )