whom 一般引导定语从句,在从句中作为宾格.例如：This is the little boy
whom Tom saved yesterday.这就是汤姆昨天救的那个小男孩.这里,whom 作为save的宾语.又如：These new neighbours,to whom I was introduced
yesterday,have come here from Beijing.这些新邻居是从北京来的,昨天我被介绍同他们认识了.这里,whom 作为be introduced to 的宾语.
pronunciation 与girl 有着所属关系,而且中心语是pronunciation,girl只是
pronunciation 的修饰语,即 the girl's pronunciation.所以用whose 表示
二者之间的所属关系.
有第二句可知,中心语就是 the boy.在定语从句中,若先行词是人,就用
who/that来引导