A:①②③
B:②③④
C:①③④
D:①②③④
My grandma's birthday is on October sixth. (对画线部分提问)
____ ____your grandma's birthday?
已知△ABC中,a,b,c分别为角A,B,C的对应边,A=30°,B=45°,a=7,则边长b为( )