生活中有许多关于热现象的例子．

（1）烤熟的山芋香气扑鼻，该现象表明____ ；

（2）水与酒精混合，总体积会变小，是因为分子间有____ ；

（3）在探究平面镜成像特点的实验中，选玻璃当平面镜的目的是____ 

Fill in the blanks with the proper forms of given words.

I helped my mother to buy some beef and three____ (potato) for supper today.

"Belt and Road"（一带一路) are the two wings of developing Asia in the____ (twenty-one) century.

Please keep____ (silence) in the concert hall because people are enjoying Lang Lang's piano performance.

Candy ____ (lay) out the tea, fruit and snacks on the table and waited for the visitors.

.With the development of technology, mobile phones are ____ (wide) used these days.

先天性行为是动物生来就具有的一种行为．决定先天性行为的是（  ）