Question

You are a deep–sea organism and your potential mates are several hundreds of kilometers away from you. Which one of the following kinds of mating signals is most likely to help them locate you?

• A. Display gestures
• B. Electric pulses
• C. Body colouration
• D. Sounds

Hint:

Match the signal to the medium: in water, \textbf{sound} carries far; in air, visual/chemical cues may dominate depending on context.

Answer 1

The Correct Option is D

Step 1: Consider deep-sea constraints.
- Very low/no light \Rightarrow visual cues (gestures, colour) are ineffective at long range.
- Seawater attenuates electrical signals strongly; electric fields are detectable only over short distances.

Step 2: Physics of signal propagation in water.
Low-frequency sound travels the farthest in the ocean, sometimes over hundreds of kilometers (SOFAR channel), making it ideal for long-distance mate attraction.

Step 3: Evaluate options.
(A) Gestures: require line-of-sight; ineffective.
(B) Electric pulses: short-range only.
(C) Body colouration: useless in darkness and at long distances.
(D) Sounds: best long-range signal in water. Final Answer:
\[ \boxed{\text{(D) Sounds}} \]