【正确答案】 C

【答案解析】fluctuate意为“波动，涨落，起伏”，例如：There is something queer about the way his temperature fluctuates these days．近些日子他的体温时高时低，这事有点奇怪。vibrate意为“(使)振动，(使) 摇摆”，例如：The ground vibrated during an earthquake．地震时大地剧烈地颤动。swing意为“(使)摇摆，(使)摇荡”，例如：A pendulum swings．钟摆来回摆动。flutter意为“(鸟等)振翼，拍翅 而飞"，例如：The bird fluttered its wings wildly but it could not get off the ground．鸟儿拼命扑打着翅膀，但仍不能飞离地面。