Which of the following describes a characteristic of arthropods?

Analyze the question: You're asked to pick the option that correctly describes a characteristic of arthropods (e.g., insects, crustaceans, arachnids, myriapods).

Concept: Phylum Arthropoda is defined by these features:

• Jointed appendages (the name means "jointed foot")
• Segmented body, usually grouped into regions such as head, thorax and abdomen
• Exoskeleton made of chitin
• Growth by moulding (ecdysis), so they cannot grow freely
• Open circulatory system and a haemocoel body cavity

Checking each option:

• A. "The organism finds it easy to grow freely": Wrong. The rigid exoskeleton limits growth, so arthropods must shed it (ecdysis) in order to grow.
• B. "The organism has a pair of jointed appendages": This is the tricky one. Arthropods have jointed appendages, but not just a pair. They have several pairs (insects have 3 pairs of legs, spiders 4 pairs, and so on). Its wording is imprecise, though it is partly true, and some students may be tempted to choose it.
• C. "The body is not divided into segments": Wrong. Arthropod bodies are clearly segmented.
• D. "The body is covered by chitin": Correct. The arthropod exoskeleton (cuticle) is made of chitin, a tough polysaccharide. It protects the animal, prevents water loss and supports the body.

Answer: D. The body is covered by chitin.

Option B is the closest distractor, but "a pair" is inaccurate, whereas D is a universally correct feature of arthropods.

Exam tip: Remember "JEC": Jointed legs, Exoskeleton, Chitin. If an option mentions chitin and an exoskeleton together, it is almost always the arthropod answer. Also watch for wording traps like "a pair" when the true feature is "pairs".