用电压表测量灯泡L₁的电压，下列电路图正确的是 [ ]

A.

B.

C.

D.

Spread spectrum simply means that data is sent in small pieces Over a number of the (46) frequencies available for use at any time in the specified range. Devices using (47) spread spectrum (DSSS) communicate by (48) each byte of data into several parts and sending them concurrently on different (49) . DSSS uses a lot of the available (50) , about 22 megahertz (MHz) .

（46）是（）

A.continuous

B.high

C.low

D.discrete