My name is Sam. I am a junior high school student. My school is close to my home, so I always go to school on foot. Classes start at 8 a.m., and I am seldom late. I like Geography best. I enjoy learning about different places in the world.

    In the morning, we usually study Chinese, Maths and English. We have our morning break at 9:50 a.m..  When the bell rings, I run to the playground with my best friends Tom and Jack. We often play games. Break ends at 10:10 a.m..

Lunch is from 11:50 a.m. to 12:30 p.m.. Afternoon classes end at 3:30 p.m. Then Tom, Jack and I take part in the school bank practice. We make great music together.

    I always have a good time at school.

①三边对应成比例的两个三角形相似;

②一个角对应相等的两个直角三角形相似;

③一个锐角对应相等的两个直角三角形相似;

④一个角对应相等的两个等腰三角形相似.

其中正确的命题是（  ）

A $\underset{①}{\overset{C{l}_2、光照}{\to }}$ （一氯环己烷） $\underset{△②}{\overset{NaOH、乙醇}{\to }}$ $\underset{③}{\overset{B{r}_{}的CC{l}_4溶液}{\to }}$ B $\stackrel{④}{\to }$