(b)
Yes, long distance TV transmission requires UHF and still higher frequencies. Ionosphere does not reflect frequencies more than 30 MHz and hence satellites are used to reflect these waves.
(c)
With reference to X-rays astronomy, X-rays are absorbed by the atmosphere. But visible and radio waves can penetrate it. Thus, optical and radio telescopes are built on the ground, while X-rays astronomy is possible only with help of the satellites orbiting the earth.
(d)
It absorbs ultraviolet radiations from the sun and prevents it from reaching the earth's surface and causing damage to life.
(e)
The temperature of the earth would be lower because of the absence of Greenhouse effect,which retains the heat from sun in the atmosphere.
(f)
The clouds produced by global nuclear war would perhaps cover substantial parts of the sky preventing solar light from reaching many parts of the globe. This would cause a winter.