Starfish, sea urchins and sea cucumbers lack a what?
Options:
- (A) characteristics
- (B) the body's largest organ
- (C) watery habitat
- (D) centralized nervous system
- (E) functioning arm
- (F) underwater life
- (G) biological diversity
- (H) epidermis and dermis
--
Let's think first: Echinoderms lack a centralized nervous system. Echinoderms include starfish, sea urchins, and sea cucumbers. Starfish, sea urchins and sea cucumbers lack a centralized nervous system.... So the answer is [(D)]

What phylum do starfish belong to?
Options:
- (A) fertile
- (B) animals
- (C) Echinoderm.
- (D) Mollusca.
- (E) Sponge.
- (F) Absorb light
- (G) Annelid.
- (H) a fish
--
Let's think first: Echinoderms have a unique water vascular system with tube feet. Each starfish arm is lined with tube feet. Starfish are echinoderms.... So the answer is [(C)]

What increases the stability of ecosystems?
Options:
- (A) overpopulation
- (B) water consumption
- (C) loose soil
- (D) Quality of life
- (E) agriculture
- (F) deforestation
- (G) ecotourism
- (H) trees
--
Let's think first: Biodiversity increases the productivity and stability of ecosystems. Ecotourism, on the other hand, can help to conserve biodiversity. Ecotourism increases the stability of ecosystems.... So the answer is [(G)]