whom       
pronoun  formal uk/huːm/ us/huːm/
B2 (作宾语时代替 who)
used instead of "who" as the object of a verb or preposition
  I met a man with whom I used to work. 我碰见了个过去曾一起工作的人。 
 He took out a photo of his son, whom he adores. 他拿出了一张爱子的照片。 
 There were 500 passengers, of whom 121 drowned. 500名乘客中共有121名溺水身亡。 
 To whom do you wish to speak? 你想找谁接电话? 
 - More examples
 - His strongest criticism is reserved for his father, whom he disliked intensely.
 - They have two grown children, both of whom live abroad.
 - He was very contemptuous of 'popular' writers, whom he described as having no talent.
 - Many of our distant cousins, whom we hadn't seen for years, came to my sister's wedding.
 - She disliked the president, whom she once described as an 'insufferable bore'.