He knew the problem was serious and undertook to look into it       he reached  the office.

A．suddenly

B．immediately

C．abruptly

D．shortly

下列关于国内特快专递邮件的分拣封发关系叙述正确的有（）。

A、各邮区中心局之间建立固定直封

B、邮区中心局与其经转范围内的开办局之间建立固定直封

C、非邮区中心局的地（市）局出口省际特快专递邮件封给其寄达局所在的邮区中心局经转

D、开办局之间建立固定直封