X-rays . are blocked by the ionosphere
are less dangerous than ultraviolet rays
have very long wavelengths
are not emitted by the sun

have very long wavelengths

Explanation:

The first  X-ray image was captured by Wilhelm Conrad Roentgen (1895), who accidentally discovered these rays while experimenting with vacuum tubes. X-rays are high-energy electromagnetic radiation with very long wavelengths (in the range of 0.01 to 10 nanometers, nm). They are shorter in wavelength than ultraviolet rays and longer than gamma rays. X-rays have energies ranging from 100 electron-volts (eVs) to 100 kiloelectron-volts (keVs). On the other hand, the radio waves are blocked by the planet's ionosphere and, therefore, they cannot reach the Earth.

answers are:

lysogenic     viral dna merges with host cell dna

lysogenic     no symptoms

lytic               viral dna takes over

lysogenic     virus does not destroy host cell

lytic               virus destroys host cell

lytic               induces symptoms of viral infection

lysogenic       cell reproduces and spreads provirus