John was one of the top students in our class, but believe it or not, he_______ passed the English exam last term.(西安市)

—Mom，dad is smoking again!—Well，let him cut it ________ gradually since old habits die hard.

The incomes of skilled workers went up. ______, unskilled workers saw their earnings fall.

It is well known to all that a machine needs fuel to run;    ,man needs food to live on.

_____, I got better and returned to work.