下列物质都含有氮元素的选项是
①核糖核酸   ②糖原 ③胰岛素    ④淀粉

为使飞机在开始滑行时就有一定的初速度，航空母舰装有弹射装置，然后在飞机发动机产生动力作用下做匀加速直线运动最后起飞．某型号的飞机经弹射系统作用后，具有144km/h的初速度，但起飞的速度须达到180km/h．该飞机提供的牵引力为1.32×1⁵N，起飞质量为2.7×10⁴kg，若飞机在跑道上匀加速100m．

读一读，连线。

①What do you like doing? ____   A.It's white and yellow.

②Do you like this pear tree? ____ B. Yes, it does.

③What colour is this flower?____    C.Yes, I do.

④Does it have long leaves? ____    D. They need water.

⑤What do the plants need?____    E. I like listening to music.

（1）解方程：$\frac{x}{2x-3}$﹣$\frac{5}{3-2x}$=4．

（2）解不等式组：$\left\{\begin{array}{c}x-2<0\\ x+5\le 3x+7\end{array}\right.$．