The language system must constantly _______a new environment and situation to survive and flourish.[ ]

The story was written in _____ easy English ____ eventhe seven-year-old boy could understand it.

When did you last hear _____ Jay? —He phoned me this morning, and we agreed____ a time and place to meet.

The professor________at 8 o’clock，but he has not shown up yet，which worries all of us.[ ]

________conversations with others is one of the secrets to ________a successful learner.