For which of the following stimuli is there no known sensory structure in living organisms?

Options

A. Pressure
B. Radio waves
C. Magnetic fields
D. Vibrations

Explanation

To solve the question of which stimuli lack known sensory structures in living organisms, we can follow these steps:

### Step 1: Understand the Types of Stimuli
We need to identify the stimuli listed in the question: pressure, radio waves, magnetic fields, and vibrations.

### Step 2: Identify Sensory Structures for Each Stimulus
- **Pressure**: Many organisms have pressure receptors. For example, humans can sense pressure through mechanoreceptors in the skin.
- **Radio Waves**: There are no known sensory structures in any living organisms that can detect radio waves.
- **Magnetic Field**: Some animals, like bats, have the ability to detect magnetic fields, which helps them navigate.
- **Vibrations**: Organisms can sense vibrations. For instance, fish have a lateral line system that detects vibrations in the water.

### Step 3: Analyze the Information
From the analysis, we can see that:
- Pressure, magnetic fields, and vibrations have known sensory structures in various organisms.
- Radio waves do not have any known sensory structures in living organisms.

### Conclusion
The correct answer to the question is **radio waves**, as there are no known sensory structures in living organisms that can detect this type of stimulus.

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