If a is a rational number, then in the following sentences: ① - A is a negative number; ② A2 is a positive number; ③ the reciprocal of a is 1A; ④ the absolute value of a is a. where () A. 1 B. 2 C. 3 d. 4 | Math enthusiast | Mathematical art

If a is a rational number, then in the following sentences: ① - A is a negative number; ② A2 is a positive number; ③ the reciprocal of a is 1A; ④ the absolute value of a is a. where () A. 1 B. 2 C. 3 d. 4

When a = 0, then - a = 0, so ① error; when a = 0, then A2 = 0, so ② error; when a = 0, a has no reciprocal, so ③ error; when a < 0, the absolute value of a is - A, so ④ error. So select D

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