纳税人应当于外出经营地开始前，持《外出经营活动税收管理证明》向外出经营地税务机关报验登记；自《外出经营活动税收管理证明》签发之日起（）日内未办理报验登记的，所持证明作废，纳税人需要向税务机关重新申请开据。

A.10

B.15

C.20

D.30

The growth of switching has (135) a new generation of network management tools that help (136) cope with the challenges, (137) them to correlate device alarms in order to (138) pinpoint root causes, or to monitor service levels without depending on IP subnet schemes. These new tools have become essential to coping with the primary (139) effect of any treatment that significantly increases network flexibility: added complexity.

A．back

B．side

C．front

D．lateral