下列句子中各有一处错处，找出并改正。

下列句子中各有一处错处，找出并改正。
1.How many pages have you read by the end of last year?
2.While I walked in the street,I saw my teacher.
3.The workers have repaired the machines just now.
4.Ther have had their lunch at twelve.
5.You have waited here since two hours.