★这句话里had是什么用法★

问题描述:

★这句话里had是什么用法★
Mrs.Richards realized that it must be the man from the Electricity Board who had come to read the metre.

整个句子的时态由realized而决定,整个句子在阐述一个过去发生的事情,所以have以had出现,这句话也可以这么说:
Mrs.Richards had realized that it must be the man from the Electricity Board who came to read the metre.
从口感上,用原句的比较多.