Short Answer

$25.$ In the IEEE $802$ physical layer frame format the $q,$ field enables the receiver to acquire an incoming OFDM signal and synchronize the demodulator.

$26.$ The need to make efficient use of transmission facilities that are typically shared among a number of communicating devices is referred to as $$

$27.$ Traffic that can adjust to changes in delay and throughput across an internet and still meet the needs of its applications is $$ traffic.

$28.$ The $$ bandwidth is the band where most of the signal energy is concentrated.

$29.$ Wireless transmission frequencies in the range of about $1$ GHz to $40$ GHz are referred to as $q,$ frequencies. Highly directional beams are possible at these frequencies.

$30.$ NRZI is an example of $q,$ encoding.