Answer: A. the decimal terminates or repeats.
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Step-by-step explanation:
A terminating decimal example would be something like 0.2 which converts to the rational number, aka fraction, 1/5. The word "terminate" means "stop", so it's any decimal that doesn't go on forever.
A repeating decimal is something like 0.33333 where the 3s go on forever, and that converts to 1/3.
If any of these conditions happen, then the number is rational.
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For something like pi = 3.14159... where there isn't a pattern and it goes on forever, then we consider this number irrational. The term "irrational" literally means "not rational". So this allows us to rule out choice C.
Choices B and D are partially true, but they only paint half the picture needed to form all rational numbers. Choice A is the most complete statement.
In other words, while choice B is technically true, it leaves out repeating decimals. Choice D is the same way but it leaves out terminating decimals. So we can rule out choices B and D.