Khẳng định (+):
She can swim very well.
We are playing football at present.
The Earth goes around the Sun.
Phủ định (-):
He is not doing his homework now.
She is not my English teacher.
We are did not go to Ha Noi last week.
Nghi vấn (?):
Did they do their homework last night?
Can you swim?
Are they playing football at the moment?