I have many books ,but _____ deals with the problem.A none of which B none of them C call of which D all of them
.The other day I was showing the boys the weekly chemistry experiment when, ________ I knew it, the mixture was bubbling over everywhere.
It was not until all the milu deer ________ that we realized we should build a natural park to protect them.
Do you remember a certain occasion ________ you were in trouble and at that moment I gave you a hand.
You may catch up with others__________you work a little harder.
__________ the students are doing their maths exercises with the help of the teacher.