#2
Will he be busy with his research work?
What did the scientists obtain?
When must you switch on the apparatus?
Who was taught how to handle these instruments?
Why do the students have to study a lot of material?
#3
The engine isn't functioning.It must be repaired.
We will repeat the experiment next month.
Our engineers put the engine in motion yesterday.
They will have reported ....
This area was explored/was being explored...