They are preparing their presentation backstage at the moment. 

(2.5 Điểm)
Their presentation are being prepared backstage at the moment.
Their presentation is being prepared backstage at the moment.
Their presentation backstage are being prepared at the moment.
Their presentation is prepared backstage at the moment.

.It's no use trying to make friends with him. (2.5 Điểm)
Making a friendship with him is worthless.
You should try to make friends with him.
There's no point in trying to make a friendship with him.
I find it difficult to make friends with him.
They often criticize Jenny for making up many stories. She doesn’t mind it

(2.5 Điểm)
They don’t mind criticizing by making up many stories about Jenny
Jenny doens’t mind being criticizing them for making up many stories
Jenny doesn’t mind being criticized for making up many stories .
Jenny doesn’t mind criticizing them for making up a lot of stories about her

It took Mary a year to do voluntary work in the mountainous and remote areas.(2.5 Điểm)
Mary takes a year doing voluntary work in the mountainous and remote areas.
Mary spent a year to do voluntary work in the mountainous and remote areas.
Mary spend a year doing voluntary work in the mountainous and remote areas.
Mary spent a year doing voluntary work in the mountainous and remote areas.