How to use ‘WHICH’ in spoken and written English

(a) For infants, small animals and objects.
Ex.- This is the baby which was lost in the theatre.
This is the dog which my friend bought from the U.S.
(b) When selection is expressed.
Ex.- Which of these television sets do you want to purchase?
(c) To refer to a sentence
Ex.- He was said to be drunk, which was not true.