Examination compositions, together with most business letters and government reports, are the main situations ____ formal language is used.

A．in which

B．on which

C．of which

D．for which

喉癌淋巴转移区多是()

A．颌下淋巴结 

B．颏下淋巴结 

C．二腹肌组淋巴结 

D．A+B 

E．B+C