To join the pairs of sentences using relative pronouns, we connect them to provide additional information about a noun without starting a new sentence. Here's how you can do it for each pair:
(a) My father gave me a pen. It has been stolen today. - My father gave me a pen which has been stolen today.
(b) Where is the man? His wallet was stolen yesterday. - Where is the man whose wallet was stolen yesterday?
(c) We met a traveller. His bag was stolen. - We met a traveller whose bag was stolen.
(d) Everyone likes the boy. He speaks the truth. - Everyone likes the boy who speaks the truth.
(e) You are the man. I wanted to see. - You are the man whom I wanted to see.
(f) The girl has come. I was saying something about her. - The girl about whom I was saying something has come.
(g) The cook saw the dog. It drank the milk. - The cook saw the dog that drank the milk.
(h) Here is the boy. The boy was shouting in the class. - Here is the boy who was shouting in the class.
Notice how relative pronouns like "which," "whose," "who," and "that" help us combine the sentences without losing any meaning. We use "which" and "that" for objects, and "whose," "who," and "whom" for people. "Whom" is used when referring to the object of the verb, while "who" is used for the subject.