ASSERTION: Microwave propagation is better than sky wave propagation.
REASON: Microwaves have frequencies 100 to 300GHz, which have very good directional properties.
A. Both Assertion and Reason are correct and reason is the correct explanation for assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but reason is incorrect.
D. Both Assertion and Reason are incorrect.

Hint: Think about all the characteristics of microwave propagation. Also, try to list out the advantages of microwave propagation over sky wave propagation. Also, see whether microwave has an advantage of having very good directional properties over sky wave propagation and hence find the answer.

Complete step by step answer:
Microwaves belong to the frequency range of 300MHz to 300GHz of the electromagnetic spectrum. ‘Micro’ in microwaves doesn’t necessarily mean that its wavelength lies in the micrometer range, it says that they are smaller than the radio waves in comparison. Line of sight propagation is a very special characteristic of microwaves. In line of sight propagation, the waves travel in a direct path from the source to the receiver. In other words, we can say that no diffraction happens for them.
Various applications of microwaves in modern technology are,
Point to point communication links, wireless networks, radar, medical diathermy, remote sensing, radio astronomy, spectroscopy, keyless entry systems, microwave radio relay networks and even in microwave ovens etc.
Microwave’s short wavelength aids the production of narrow beams of microwaves which further has an advantage of not interfering with nearby equipment using the same frequency and also allows frequency reuse by nearby transmitters.
Along with being easily focused and allowing frequency reuse, they have high frequency that aids broad bandwidth and high data transmission rates. Also due to atmospheric ducting, they follow the curvature of the Earth and hence reach beyond the horizon.
Due to all the above mentioned characteristics of microwaves specially, its directional properties, Microwave propagation is better than sky wave propagation. Therefore, assertion and reason is true with reason being the correct explanation for the assertion.

So, the correct answer is “Option A”.

Note:
Sky wave is however not limited by the curvature of earth hence there is no obstruction for its propagation beyond the horizon. They are mostly used in the shortwave frequency bands. Radio wave propagation is another name for sky wave propagation.