I feel it hard to keep up with myclassmates in study and sometimes I lose heart. But whenever I want to ________, my teacher always encourages me to work harder.

The project is based on an agreement, one of ________ purposes is to ensure that the project can be accomplished before the deadline.

How much difficulty has the team had_______ this problem—_______．The members are all good problem solvers.

My sister has a beautiful ________ and she sings very well.

Class is to begin in a minute , but the teacher still hasn’t .