参考答案：B

解析： 近义辨析。
这四个词都指“投，抛，掷”。cast指转向或引向：All eyes were cast uponthe speaker．所有目光皆投注在说话者身上。toss：指以迅猛的速度突然移动或抬起(头)：tossing their heads in sprightly dance在轻盈活泼的舞步中抬起他们的头。fling指摆动(身体一部分)：She flung back her head proudly．她傲气地把头一扬。throw指发出，投射：She threw me a look of encouragement．她向我投来鼓励的目光。