______ their homework, these three students have to stay in the classroom for another thirty minutes.
| A．Not finishing | B．Not finished |
| C．Having not finished | D．Not having finished |
—How do you deal with the disagreement between the company and the customers?
—The key _______ the problem is to meet the demand _______ by the customers.
| A．to solving, making | B．to solving, made |
| C．to solve, making | D．to solve, made |
In order to make our city green, _______.
| A．it is necessary to have planted more trees | B．many more trees need to plant |
| C．our city needs more trees | D．we must plant more trees |
In order not to be disturbed ,I spent three daysin my study.
| A．locking | B．locked | C．to lock | D．lock |
He sat back on the chair, took a book and began to read, ___.
| A．being looked at ease | B．looked rather at ease |
| C．to look rather at ease | D．looking rather at ease |
David apologized for ______ to inform me of the change in the plan.
| A．his being not able | B．him not to be able |
| C．his not being able | D．him to he not able |