不锈钢采用硝酸酸洗的目的是使带钢表面形成一层（），以提高后续使用的耐腐蚀性。
参考答案：钝化 膜
In the past few years there ________ great changes in my hometown.
A．has been
B．have been
C．have had
D．were
按要求完成句子（5分）
小题1:I go to school five days a week. (对画线部分提问)
小题1:
________ _______ you go to school in a week?
小题2:Tom did something interesting last weekend.(改为一般疑问句)
小题2:
__________ Tom ________ ________ interesting last weekend?
小题3:She usually watches TV for over two hours a day. (改为同义句)
小题3:
She usually watches TV for two hours a day.
小题4:Lisa stayed in Suzhou for a month. （对划线部分提问）
小题4:
________ _______ _______Lisa ______in Suzhou?
小题5:Junk food is unhealthy for us. (改为同义句)
小题5:
Junk food_______ ________ ________our health.
