Directions: For the Assertion (A) and Reason (R) given below, choose the correct alternative. Assertion (A): Bats can fly and move about in the night. Reason (R): Bats emit ultrasonic sound waves.

Introduction / Context:
This question relates to animal behaviour and sensory biology. It asks how bats are able to fly in the dark at night without colliding with obstacles. The assertion–reason format is used to connect this ability with the emission of ultrasonic sound waves, a key feature of bat navigation.

Given Data / Assumptions:

• Assertion (A): Bats can fly and move about in the night.
• Reason (R): Bats emit ultrasonic sound waves.
• We assume school level biology knowledge about echolocation in bats.
• The task is to decide if A and R are true and whether R explains A.

Concept / Approach:
Bats are nocturnal animals. They navigate and hunt in darkness using a system called echolocation. They emit very high frequency sounds (ultrasonic waves) that humans cannot hear. These sounds reflect off objects and return as echoes, which bats interpret to understand their surroundings. This allows them to avoid obstacles and capture flying insects at night.

Step-by-Step Solution:
Step 1: Evaluate Assertion (A). Bats are well known for being active at night. They fly from their roosts in caves, trees or buildings after dark, searching for food. Therefore, the assertion that bats can fly and move about in the night is true.Step 2: Evaluate Reason (R). Scientific studies have shown that many bat species produce ultrasonic calls far above the range of human hearing. These calls are directed into their environment and the returning echoes are processed by their specialised hearing system. So R is also true.Step 3: Check whether R explains A. The ability to emit ultrasonic wave pulses and interpret the returning echoes is the main reason bats can navigate reliably in complete darkness. Their echolocation system substitutes for vision when light is low, allowing safe flight at night.Step 4: Thus the reason does not just relate to the assertion but is its core biological explanation. Both A and R are true and R explains A.

Verification / Alternative check:
If bats did not use echolocation, they would have much more difficulty flying in the dark, especially in cluttered environments such as forests or caves. Observations using special microphones and experiments blocking echolocation show that bats rely heavily on these ultrasonic calls. This supports the explanatory connection claimed in the question.

Why Other Options Are Wrong:
Option b denies the explanatory link even though echolocation is clearly the mechanism behind nocturnal navigation. Options c and d require one of the statements to be false; this conflicts with well known biological facts that bats are nocturnal fliers and emit ultrasonic sounds.

Common Pitfalls:
Some students may remember that bats “cannot see” and believe they rely only on sound, but many bats can see reasonably well. The key point here is that ultrasonic echolocation is the specialised adaptation that allows them to fly and hunt effectively in darkness. Understanding this helps avoid confusion about how vision and hearing both contribute to bat behaviour.

Final Answer:
The correct choice is that both Assertion (A) and Reason (R) are true and R is the correct explanation of A.