There is no alternative to study regularly for good result.

There is no doubt about his honesty.

There is no doubt about it.

There is no mother but loves her child.

There is no mystery greater than misery

There is no rose but has a thorn. (Affirmative) = Every rose has a thorn

There is nobody but knows about the Royal Bengal Tiger of Sundarban.

There is none to look after her. 

There lived a certain king. 

There was dust on the floor.

They are quite mistaken.

They came home while I was studying.

They elected him captain.   = He was elected captain by them.

They elected me secretary. (Passive) = I was elected secretary by them.

They had dug the pond=The pond had been dug by them.