Choose the correct form.
They seldom quarrel / are quarrelling.
The Earth moves round the Sun / is moving.
Now they are crossing / cross the street.
Birds fly / are flying to warm countries in autumn.
The children often laugh / are laughing at their funny little friend.
They seldom quarrel. - Present Simple
The Earth moves round the Sun. - Present Simple
Now they are crossing the street. - Present Continuous
Birds fly to warm countries in autumn. - Present Simple
The children often laugh at their funny little friend. - Present Simple