which is enabled by the context of（）．

单项选择题All traffic，be ite-mail or streaming video，travels via a method called packet switching，（）parcels out digital data into small chunks，or packets，and sends them over a network shared by countless users.

A.so
B.which
C.and
D.who

单项选择题But the hard ware is designed to use even less power than other schemes，making itespecially appropriate for such things as RFID tags，which must work for years （） any external power source.

A.with
B.without
C.as
D.than