The main advantage of microwave is that
A. Highly directive
B. Moves at the speed of light
C. $\dfrac{S}{n}$ ratio greater
D. High penetration power

Hint:In order to solve this question, We should know that Microwaves are one of the types of electromagnetic radiations whose wavelength lies in the region of one meter to one millimetre and here we will discuss each option one by one to know that, which quality makes the microwave more advantageous over others.

Complete answer:
Considering option (A) Highly directive. Since directivity is inversely related to the wavelength of the electromagnetic waves and microwaves having the least range of wavelength which is one meter to one millimetre so, it has highly directive and this is one of major advantages over other waves.
option (B) Moves at the speed of light. Since all electromagnetic waves move at the speed of light, this is neither an advantageous factor nor a drawback of microwaves.

option (C) $\dfrac{S}{n}$ ratio greater. Here, $\dfrac{S}{n}$ represents the ratio of signal power to noise power and microwaves don’t have very large values of this factor, so it doesn’t have this advantage.
option (D) High penetration power. Gamma rays have the highest penetrating power, so it also is not the advantage of microwaves. So, the only advantage of a microwave is its highly directive.

Hence, the correct option is (A).

Note: It should be remembered that, due to the highly directivity of microwaves, microwaves are used in point to point communication, radar, satellite and spacecraft communication and in everyday life most common use is coking, ovens use microwaves for cooking the food material inside it.