What's the difference between mandibulates and chelicerates?

Problem 8SA: Distinguish between chelicerates and mandibulates. Two major groups of marine arthropods are mandibulates and chelicerates. Chelicerates typically have a pair of oral parts called chelicerae but do not have mouthparts for any chewing. ... Mandibulates have parts called mandibles that are used for chewing.

the corpus luteum secretes estrogens and progesterone. the latter hormone causes changes in the uterus that make it more suitable for implantation of the fertilized ovum and the nourishment of the embryo. if the egg is not fertilized, the corpus luteum becomes inactive after 10–14 days, and menstruation occurs.

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it's not c. i took the quiz and got it wrong. so my best guess is b.

have a great day, and hope this .