情景： 你是小明，是班里的学习委员，到办公室去交英语作业，老师不在。 任务： 请你用英语给老师写一张50字左右的便条。告诉他： ·你何时来的； ·作业没有收齐； ·作业未收齐的原因。 请用下面格式。 Door teacher, .... Xiao Ming

[A] Because there is a bridge over the Cam. [B] Because the river was very well known. [C] Because there is a river named Granta.