用久了的灯泡会发黑，是因为钨丝发生了（　　）

若$\overrightarrow{a}$，$\overrightarrow{b}$均为非零向量，则$\overrightarrow{a}$•$\overrightarrow{b}$=|$\overrightarrow{a}$||$\overrightarrow{b}$|是$\overrightarrow{a}$与$\overrightarrow{b}$共线的（　　）

完形填空。

    On Thursday evening, Jack goes to bed early. Then he sees a rabbit. Jack doesn't know1it is from. He doesn't have a pet rabbit at home.     “Come on,” says the rabbit. “Let's go to town!” “You can2?” Jack asks. “Yes,” the rabbit answers. “Come 3me.” Then the rabbit goes out of the4Jack goes with it.

    They get to a zoo. In the zoo, a(n)5 is playing the guitar under a tree. “Let's dance!” says the rabbit. Jack 6with the rabbit. And he sees the moon is dancing, too. Jack wants to tell the rabbit about this,7he can't find it. And he doesn't see the zoo or the lion. He sees his8! “Jack, get up! You have to go to school!” says his mom. Jack smiles and he can't wait to9his mom about the dream. It's so10.

“一带一路”国际合作高峰论坛于2017年5月14日至15日在北京举行，在论坛召开之际，福田欧辉陆续向缅甸仰光公交公司交付1000台清洁能源公交车，以2017客车海外出口第一大单的成绩，创下了客车行业出口之最，同时，这也是在国家“一带一路”倡议下，福田欧辉代表“中国制造”走出去的成果．预计到2019年，福田公司将向海外出口清洁能源公交车达到3000台．设平均每年的出口增长率为x，可列方程为（   ）

60℃时，100g水溶解20.94g氢氧化钡恰好饱和，则氢氧化钡属于（   ）