The correct answer is A. two pairs of antennae. Explanation of the Correct Answer Insects are a class of arthropods characterized by several distinct features. One of the defining characteristics of insects is that they possess one pair of antennae, not two. This is a key feature that differentiates insects from other arthropods, such as crustaceans, which typically have two pairs of antennae.

1. Antennae: Insects have a single pair of antennae that serve as sensory organs. These antennae are crucial for detecting environmental cues, such as smells and vibrations. The presence of only one pair of antennae is a hallmark of the insect class (Insecta).

Why the Other Options are Incorrect or Weaker B. Jointed appendages: - This statement is true. Insects, like all arthropods, have jointed appendages. This feature allows for greater flexibility and mobility, which is essential for their survival. The jointed legs and mouthparts enable insects to perform various functions, such as walking, feeding, and mating. C. Exoskeleton: - This statement is also true. Insects possess an exoskeleton made of chitin, which provides structural support and protection. The exoskeleton is a defining characteristic of all arthropods, allowing them to maintain their shape and protect against predators and environmental hazards. D. Three pairs of legs: - This statement is true as well. Insects are characterized by having three pairs of legs (six legs in total). This is another distinguishing feature of insects, setting them apart from other arthropods, which may have different numbers of legs. Summary of Key Points

• Insects have one pair of antennae, which is a defining characteristic that distinguishes them from other arthropods.
• They possess jointed appendages, which provide flexibility and mobility.
• Insects have a protective exoskeleton made of chitin.
• They are characterized by having three pairs of legs (six legs total).

Revision Summary

• Insects have one pair of antennae, not two.
• They possess jointed appendages for movement and feeding.
• Insects have a chitinous exoskeleton for protection.
• They are defined by having three pairs of legs (six legs total).

Understanding these characteristics is crucial for identifying insects and differentiating them from other arthropods.