Which organism is an arachnid, not an insect?

• A. Spider
• B. Sequence
• C. Financial Security
• D. Teaching Moments

Answer: (A)

The idea being tested is how to tell arachnids from insects based on body plan and legs. Arachnids, like spiders, have eight legs and typically two main body parts, and they usually lack antennae and wings. Insects have six legs, three body segments, and usually antennae (and often wings). A spider clearly fits the arachnid pattern: it has eight legs and a two-part body, not six legs and three segments with antennae. The other options aren’t living animals at all, so they can’t be arachnids or insects. So the spider is the correct choice.