设F是双曲线C：-=1的一个焦点，若双曲线C上存在点P，使线段PF的中点恰为其虚轴的一个端点，则双曲线C的离心率为 .
There was never any time for Kate to feel lonely, __________ she was an only child. A．ever since B．now that C．even though D．even as
_________at the cafeteria before, Tina didn’t want to eat there again. A. Having eaten B. To eat C. Eat D. Eating
如图所示，在倾角θ=37°的足够长的固定的斜面底端有一质量m=1.0kg的物体，物体与斜面间动摩擦因数μ=0.25。现用轻细线将物体由静止沿斜面向上拉动，
They will arrive _______China _______September 2nd. A. in, on B. at, from C. in, in D. at, on
某跨国公司在中国某市投资建设自动化的食用油生产厂，用国际市场上的大豆为原料，生产食用油，跨国公司在中国投资建设食用油生产厂，主要是因
的展开式中，
的系数为 ．