题目

The insanely popular song ‘Gangnam Style’ from South Korean recording artist PSY has just become the most watched video on YouTube ever, garnering more than 808 million views on the popular media site. The distinction was previously held by another pop heavyweight, Justin Bieber, whose song ‘Baby’ had a little more than 804 million views at press time. PSY made the announcement on his Twitter page earlier today. Since its release, the song has defeated such other popular videos as Jennifer Lopez’s ‘On the Floor,’ Eminem's ‘Love the Way You Lie’ and LMFAO’s ‘Party R一个物体在三个共点力 F1、F2、F3 作用下做匀速直线运动。现保持F1、F2不变,不改变F3的大小,只将F3的方向顺时针转过90°。对于物体以后的运动,下列说法中正确的是     A.物体的动能一定变化 B.力F3一定对物体做负功 C.物体一定做匀变速曲线运动 D.物体可能做匀变速直线运动
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