please help me to complete this dialogue.thank you.
问题描述：
please help me to complete this dialogue.thank you.
A:it's a fine day today,isn't it?
B:________?it's wonderful after the downpour.
A:how nice seeing__________back again.the air is so fresh.
B:let's hope it stays nice for the whole week.
A:well,the weather is terribly changeable at this time of the year.we don't know what it's going to be like tomorrow _________we listen to the latest weather report on the radio.
答
B:why not
A:sun
A:unless