请用适当的词完成下面的短文,每个空只能填写一个形式正确、意义相符的单词。
A 14-year-old Chinese boy SunYixiao was____his way home last Tuesday evening after school. When he was in the lift, it suddenly stopped. Feeling scared at first, the teenager decided to help____out. Sun tried to open the lift door, but he gave up the idea later and leaned against the wall, because he thought the____ may fall down suddenly. He then pressed all the buttons in the hope of getting the lift work again,____it didn't work. Sun then pressed the “stop” button to lock the lift to ____sure it would not fall. Without a cellphone at hand, Sun tried shouting____to get the attention of people outside, but no one answered as time went by. The young boy didn't give up____.He sent a note through the door with the message and hoped someone would____it up and help him out. After doing all these, the boy knew it might take a____time before someone found him. So he decided to do his homework. Soon after he finished his homework, he was saved at last.
On Weibo, many netizens (网民) spoke highly of the boy， because he could keep calm in the face of such____dangerous situation. We should learn from him.
)为一种高分子树脂，其合成路线如下： 已知：①A为苯甲醛的同系物，分子中无甲基，其相对分子质量为134；