A SONAR (Sound Navigation and Ranging) uses ultrasonic waves to detect and locate objects under water. In a submarine equipped with a SONAR, the time delay between generation of a probe wave and the reception of its echo after rejlection from an enemy submarine isfound to be 77 s. What is the distance of the enemy submarine?

To find the distance of the enemy submarine, we can analyze the principle of SONAR (Sound Navigation and Ranging).
A SONAR transmitter sends out an ultrasonic wave into the water. This wave travels to the underwater target (the enemy submarine), reflects off its surface, and returns to the receiver. Because the wave travels to the target and back, the total distance covered by the wave is twice the actual distance to the target.

Let $d$ be the distance of the enemy submarine from the transmitter.
Therefore, the total distance traveled by the sound wave is:
$\text{Total distance}=2d$
Let $v$ be the speed of sound in water, and $t$ be the time delay between sending the probe wave and receiving its echo.

We are given the following values:
Time delay, $t=77\text{s}$
Speed of sound in water, $v\approx 1450\text{m/s}$ (standard value in water)

Using the relationship between distance, speed, and time:
$2d=v\times t$
Rearranging the formula to solve for the distance $d$:
$d=\frac{v\times t}{2}$

Substitute the given values into the equation:
$d=\frac{1450\times 77}{2}$
$d=725\times 77$
$d=55825\text{m}$

Thus, the distance of the enemy submarine is 55825 m, which corresponds to the correct option.