Which choice is a real number?

Which choice is a real number?

• A. 0^1
• B. √(-1)
• C. i
• D. -i

Answer: (A)

Real numbers are numbers without imaginary parts. Among these expressions, only the first one results in a real number. Raising 0 to the first power gives 0, and 0 is a real number. The square root of a negative number, written as √(-1), is defined as an imaginary unit i, and both i and -i are purely imaginary numbers, not real. Since real numbers do not include these imaginary values, the only real result here is 0.

Real numbers are numbers without imaginary parts. Among these expressions, only the first one results in a real number. Raising 0 to the first power gives 0, and 0 is a real number. The square root of a negative number, written as √(-1), is defined as an imaginary unit i, and both i and -i are purely imaginary numbers, not real. Since real numbers do not include these imaginary values, the only real result here is 0.