Read and write.

1. A:        ?

    B: I'm 160 cm tall.    

2. A:                                     ?

    B: My sister is 20 years old.

3. A:                                     ?

    B: I ate good food yesterday.

4. A:                                     ?

    B: No, I didn't go swimming.

5. A:                                     ?

    B: We went to Nantong.

6. A:                                     ?

    B: I feel sick.

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) .

（48）是（）

A.splitting

B.combining

C.packing

D.compacting