Which of the following about modern echinoderms is true?

Question

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All modern echinoderms have a water vascular system, which helps them with movements such as crawling and feeding. B) Most modern echinoderms are not crinoids, but include starfish, sea urchins, and sea cucumbers. C) While many echinoderms have arms, not all do. For example, sea urchins and sand dollars do not have arms. D) Most echinoderms have an internal skeleton made of calcium carbonate, rather than an external skeleton. E) While many echinoderms use tube feet for mobility, there are some that do not, such as sea lilies (crinoids).

Which of the Following About Modern Echinoderms Is True