The librarian had to ______ the naughty boy in order to let others concentrate on their books.

A．revolve

B．surround

C．silence

D．adopt

为市场交易的基本原则的是（）

A、提高职业技能

B、双向选择比

C、知情权

D、出具凭证和单据

E、自愿、平等、公平、诚实信用