Tom:Lets go picnic this Saturday.Susan: Dont you think its still a bit chilly at this time

Tom:Lets go picnic this Saturday.Susan: Dont you think its still a bit chilly at this time of year？Tom: ______.

A．No wonder

B．Cheer up

C．Up to you

D．Come on

请帮忙给出正确答案和分析，谢谢！