What class do all insects belong to?

Insects belong to the class Insecta within the Phylum Arthropoda. This classification is based on specific characteristics unique to insects, such as a segmented body divided into three main parts: the head, thorax, and abdomen. Additionally, insects typically have six legs and, in most cases, they possess wings at some stage of their life cycle.

The other classifications mentioned are separate classes within the same phylum. Arachnids (like spiders and scorpions) belong to the class Arachnida, myriapods (which include centipedes and millipedes) are part of the class Myriapoda, and crustaceans (such as crabs and lobsters) are classified under Crustacea. Each of these classes represents distinct groups of arthropods with their unique anatomical and physiological features, which is why Insecta is the only correct answer for the question regarding the class to which all insects belong.