An aquarium contains Bettas, Guppies, and Neon Tetras. In total there are 18 fish in the aquarium. Less than 10 of the fish are Guppies. How many Bettas are in the aquarium?
(1) The ratio of Bettas to Neon Tetras is 5:3
This means the number of Bettas and Neon Tetras must be in multiples of 5 and 3, respectively. Possible values are (5,3), totaling 8, or (10,6), totaling 16.
If Bettas and Neon Tetras were 5 and 3, the number of Guppies would be 10, which contradicts the given condition that there are fewer than 10 Guppies.
Therefore, the only valid possibility is Bettas = 10 and Neon Tetras = 6. Sufficient.
(2) There are 4 more Neon Tetras than there are Guppies.
This alone does not uniquely determine the number of Bettas, as multiple valid combinations exist. Not sufficient.
Answer: A.
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