设△ABC的内角A、B、C所对边的长分别为a、b、c，且有2sinBcosA=sinAcosC+cosAsinC．

（Ⅰ）求角A的大小；

（Ⅱ）若b=2，c=1，D为BC的中点，求AD的长．

— My room gets very cold at night.

— __________.

A．So is mine

B．So mine is

C．So does mine

D．So mine does