Peter received a letter just now ____ his grandma would come to see him soon.

问题描述:

Peter received a letter just now ____ his grandma would come to see him soon.
A.said
B.says
C.saying
D.to say
此句的逻辑主语是谁

saying 现在分词短语作后置定语修饰letter ,说明信的内容
彼得刚收到一封信,信上说他的奶奶要来看他