Which of the following electromagnetic waves are used in telecommunication?

Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
$(a)$ $21 \; cm$ (wavelength emitted by atomic hydrogen in interstellar space).
$(b)$ $1057 \; MHz$ (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).
$(c)$ $2.7 \; K$ (temperature associated with the isotropic radiation filling all space; thought to be a relic of the 'big-bang' origin of the universe).
$(d)$ $5890 \; \mathring{A} - 5896 \; \mathring{A}$ (double lines of sodium).
$(e)$ $14.4 \; keV$ (energy of a particular transition in $^{57}Fe$ nucleus associated with a famous high-resolution spectroscopic method, Mossbauer spectroscopy).

Fingerprints on a piece of paper may be detected by sprinkling fluorescent powder on the paper and then looking at it under:

The frequencies of $X-$rays,$\gamma-$rays and ultraviolet rays are respectively $p, q$ and $r$. Then which of the following is correct?

Write the source of ultraviolet waves.

The frequency range from $3 \times 10^9 \, Hz$ to $3 \times 10^{10} \, Hz$ is known as: