如图所示，质量为m的物体用细绳拴住放在水平粗糙传送带上，物体距传送带左端距离为L，稳定时绳与水平方向的夹角为θ，当传送带分别以v1、v2的速度作逆时针转动时(v1<v2)，稳定时细绳的拉力分别为F1、F2；若剪断细绳后，物体到达左端的时间分别为tl、t2，下列关于稳定时细绳的拉力和到达左端的时间的大小一定正确的是 （     ）

    On a cold winter day, a fox ____  mother bear that he would teach her how to fish. As she____ to learn, he took her to a hole in the ice, and told her to put her tail down in the water. He told her to keep the tail there for____ .  Then____ she pulled the tail out of the water, she would find fish around the tail. The bear was foolish enough to believe____ the fox said. She sat for a long time with her tail in the water. She was ____ the fish. But when she____  to pull her tail lout of the water, she found that it was frozen in the ice. She asked the fox to pull her out. But he laughed to himself and ____ . so she called father bear to help her. Father bear came. He pulled hard and ____ got her out, but a part of her tail was in the ice. That is____ people find the bear’s tail so short.