one day,Mr.smith 1 out for a walk in the street.he 2 about a

one day,Mr.smith 1 out for a walk in the street.he 2 about a maths problem.he 3 to work it out.just then he 4 a blackboard in front of him.he 5 to write the problem with a chalk on it.then the blackboard 6 a little.Mr.smith moved with it.but the blackboard moved faster.he 7 not 8 up with it.he 9 and saw the"blackboard" before him.why?it 10 the back of the carriage!
1.A go B goes C was go D went
2.was think wasthinking think was seeing
3.wanted began begins was begin
4.sees saw looks looken
5.began start can could
6.moving moved move stopped
7.can does do could
8.stand keep looked got
9.looked lookat looked up looked down
10.is had has was