当CPU通过8251A与调制解调器相连时，其中信号DSR表示调制解调器是否准备好，CPU是通过( )方式获取DSR的值。

A．DSR信号直接送到CPU

B．当DSR信号有效时，8251A向CPU发中断请求

C．CPU读8251A的状态寄存器

D．CPU无法知道DSR信号的状态

The old man remained seated on the grass with his thoughts ________ the faith that the boy is worth ________ .

A．concentrated in ; adopting

B．focused on ; being adopted

C．attracted to ; to be adopted

D．concentrated on ; adopting