如图，在Rt△ABC中，∠C＝90°，AC＝3，BC＝5，分别以点A、B为圆心，大于 $\frac{1}{2}$ AB的长为半径画弧，两弧交点分别为点P、Q，过P、Q两点作直线交BC于点D，则CD的长是____．

已知点P（1，a）与Q（b，2）关于x轴成轴对称，又有点Q（b，2）与点M（m，n）关于y轴成轴对称，则m﹣n的值为（  ）

如图所示，一个不记重力质量为m、带电荷量为q的粒子，从两平行板左侧中点沿垂直场强方向射入，当入射速度为v时，恰好穿过电场而不碰金属板．要使粒子的入射速度变为 $\frac{v}{2}$ 仍能恰好穿过电场，则必须再使（   ）

用所给动词的正确时态、语态填空
⑴Be quiet, please ! The baby____ (sleep).
⑵—What does Frank often do at weekends?
—He often____ (go) to the cinema with his parents.
⑶Andy ____ (argue) with his brother when I went to see him yesterday.
⑷She ____ (be) to her hometown several times.
⑸____ (play) computer games too much is bad for your eyes.
⑹Lucy tried ____(not make) too many mistakes in the exam.
⑺He ____  to us as soon as he gets there. (write)
⑻By the time I got outside, the bus____ (leave).
⑼I'm sure I ____  her four years ago. (see)
⑽In summer,  Miss Xia would rather ____  (stay) at home than go out.

中华民族在近百年艰苦卓绝的伟大复兴历程中，通过“中国新生”和“伟大转折”实现了国家的独立与富强。“中国新生”和“伟大转折”分别是指（    ）