给出下列命题：

①存在实数α，使sinαcosα=$\frac{\sqrt{3}}{2}$

②函数y=sin($\frac{3}{2}\mathrm{\pi }$-x)是偶函数

③x=$\frac{\mathrm{\pi }}{8}$是函数y=cos(2x+$\frac{3}{4}\mathrm{\pi }$)的一条对称轴方程

④若α、β是第一象限的角，且α＜β，则sinα＜sinβ

其中正确命题的序号是____

⑴Are you going to meet some friends?____          A. I'm going to swim.

⑵What are you going to do today?____                B. Yes, we are

⑶What is Tony going to do?____                           C. He's going to play football.

⑷How many days are there in a week?____           D. It's three o'clock.

⑸What time is it now?____                                     E. There are seven days.

清明小长假期间，小明一家驾车通过扩建后的眉山岷江二桥，大桥全长1.6km，桥头立着如图所示的两个标志牌．如果一辆匀速行驶的载重汽车恰好达到两标志牌的最大限定值，该车通过桥中央时对桥面的压力为____ N，为了不违反交通规则，他们驾车通过该桥所用时间为____ s．（g取10N/kg，车长不计）