The number of students in our class ____ 50. And a number of students _____ planting trees now.

Mr Smith was really helpful when you were in financial difficulty during those years— Definitely I can never appreciate his kindness ________

On seeing the _______ scene, the little girl was so _______ that she burst out crying.

Paper money was in_______use in Chinawhen Marco Polo visitedthe country in________thirteenth century.

Will you stay for lunch?——Sorry，. My brother is coming to see me.