分层限时跟踪练
Ⅰ.单句语法填空
1．These early settlers owed(owe) their survival to hard work and determination to succeed.
2．When the clock strikes(strike) six，the children go home for dinner.
3．We are working on the assumption(assume) that it was a gas explosion.
4．There is not much difference(differ) in price between the two computers.
5．It is forbidden(forbid) to sell alcohol to those under the age of 18 here.
Ⅱ.单句改错
