题目

 The firemen told us the great difficulty they had had _____ the fire _____. A. to get; under control B. getting; controlled C. got; controlled D. getting; to control 答案：B物体受两个力作用，其中Ｆ１＝8Ｎ，Ｆ２＝6Ｎ，已知这两个力作用在同一直线上，则该物体所受的合力为                            （    ） Ａ　一定为14Ｎ　　         Ｂ　一定为2Ｎ　　 Ｃ　一定与Ｆ１同向　　      Ｄ一定与Ｆ２方向