The process of increasing the strength of a signal using an electronic circuit is called

For television broadcasting,the frequency employed is normally in the range of,

The bandwidth of an audio signal is approximately:

When the receiving antenna is on the ground,the range of a transmitting antenna of height $980 \ m$ is (Radius of the earth $= 6400 \ km$) (in $km$)

Match List-$I$ with List-$II$:

List-$I$ (Layer of atmosphere)	List-$II$ (Approximate height over earth's surface)
$(A)$ $F_1$-Layer	$(I)$ $10\,km$
$(B)$ $D$-Layer	$(II)$ $170-190\,km$
$(C)$ Troposphere	$(III)$ $100\,km$
$(D)$ $E$-Layer	$(IV)$ $65-75\,km$

Choose the correct answer from the options given below:

Statement-$1$: Sky wave signals are used for long-distance radio communication.
Statement-$2$: These signals are generally less stable than ground wave signals.