th hastwo______ , both of whom are teachers in a school.

下列各句中，没有语病的一句是（ ）

oft, in a _______ from tradition, has already released similar touch-friendly Office apps for Apple Inc’s iPad and iPhone.

Jack ran ______ to catch up with other students.

Though he started late,Mr.Guo played the piano as well as,if______,Miss Liu.