Conjunctions are used to groups of words, phrases and clauses together. The most common conjunctions are and, or and but.
And means also, added to:
Please speak slowly and clearly.
She plays piano and guitar.
Or is used to introduce another possibility:
Shall we go to the cinema or bar?
Are you interested or not?
But is used to introduce something new that you say, especially something that is different or the opposite from what you have just said:
I want to go, but I have to work.
She didn't send me a birhday card, but she did phone me.
Now choose the word which best fits each sentence: