Some crustaceans feed on
Options:
- (A) phytoplankton
- (B) fungi
- (C) refraction of light
- (D) heat energy
- (E) an organism's body
- (F) carbon
- (G) algae
- (H) salt and water.
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Let's think first: Zooplankton are tiny animals that feed on phytoplankton. Many zooplankton are crustaceans. Some crustaceans feed on phytoplankton.... So the answer is [(A)]


Which of the following has the most complex nervous system?
Options:
- (A) animals
- (B) nerves
- (C) fur seals
- (D) humans
- (E) elephants
- (F) Jellyfish
- (G) bears
- (H) kalenchoes
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Let's think first: Most invertebrates have a more complex nervous system. Jellyfish and insects are invertebrates. Jellyfish have a more complex nervous system.... So the answer is [(F)]


Some what will kill their host, while others won't?
Options:
- (A) barnacles
- (B) producers
- (C) scavengers
- (D) insects
- (E) cigarettes
- (F) fungi
- (G) plants
- (H) leeches
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Let's think first: Some parasites kill their host, but most do not. Leeches are external parasites. Some leeches will kill their host, but most do not.... So the answer is [(H)]