The passage mainly explains

how bats use sound and echoes to find things in the dark (The passage explains echolocation: how bats read echoes to sense their surroundings in the dark.)

What does the delay of an echo tell the bat?

How far away the object is (The text says a nearer object echoes back sooner, so 'the delay tells the bat how far away something is'.)

Why can bats hunt where our eyes fail?

They use echoes, which do not need light (Bats sense by sound bouncing back, so they work 'in complete darkness' where sight, needing light, fails.)

In this passage, 'echolocation' means

finding where things are by their echoes (The text defines it: 'finding the location of things by their echoes'.)

Seeing With Sound: Level 3 Reading Comprehension Questions

Many bats hunt in complete darkness, chasing insects through the night air without ever seeing them. They manage this by using sound the way we use light. As a bat flies, it sends out a stream of high, sharp calls, most of them too high for human ears to hear.

When a call strikes an object, part of the sound bounces back as an echo. The bat listens for these returning echoes and reads them closely. A nearer object sends its echo back sooner, so the delay tells the bat how far away something is. Changes in the echo hint at the object's size and even the direction it is moving. From a rapid stream of echoes, the bat builds a picture of the space around it.

This method is called echolocation: finding the location of things by their echoes. It is so precise that a bat can catch a single insect in midair or weave through branches it cannot see. Where our eyes fail in the dark, the bat has learned to let sound do the seeing.

Comprehension questions