Given below in the left column are different modes of communication using the kinds of waves given in the right column.
(1) Optical Fibre Communication    (P) Ultrasound
(2) Radar                                          (Q) Infrared Light
(3) Sonar                                           (R) Microwaves
(4) Mobile Phones                            (S) Radio Waves
From the options given below, find the most appropriate match between entries in the left and the right column.

We begin by recalling the typical electromagnetic (or mechanical) waves employed in each listed technology.

Optical fibre links guide light through glass fibres. In practice the light used is not in the visible band; instead it lies in the infrared region because attenuation there is minimum. So,

$$\text{Optical Fibre Communication}\; \longrightarrow\; \text{Infrared Light (Q)}.$$

Radar stands for RAdio Detection And Ranging. It relies on short-wavelength radio waves so that the reflected beam can resolve small objects. These short radio waves fall in the microwave band. Thus,

$$\text{Radar}\; \longrightarrow\; \text{Radio Waves (S).}$$

A sonar set emits sound pulses well above the audible limit (20 kHz). Such sound is called ultrasound. Therefore,

$$\text{Sonar}\; \longrightarrow\; \text{Ultrasound (P).}$$

Mobile phones transmit and receive electromagnetic waves in the UHF (Ultra-High-Frequency) part of the spectrum, which is popularly grouped under microwaves. Hence,

$$\text{Mobile Phones}\; \longrightarrow\; \text{Microwaves (R).}$$

Collecting all four associations, we have

$$\begin{aligned} 1 &-;; Q,\\ 2 &-;; S,\\ 3 &-;; P,\\ 4 &-;; R. \end{aligned}$$

Looking at the given options, the set $$(1-Q,\;2-S,\;3-P,\;4-R)$$ appears only in Option A.

Hence, the correct answer is Option A.