Which of the following is a possible sum of the complex numbers √-9 (September 2023 - G01)

Correct answer: A. 7i.
To clarify, the sum of two complex numbers is obtained by separately adding their real and imaginary parts. In this case, both √-9 and √-16 are purely imaginary numbers, meaning they have no real parts (no numbers without the "i"). Therefore, the sum of the imaginary parts is 3i + 4i = 7i.

However, the answer choices are presented in a simplified form, where the imaginary unit "i" is removed. This simplification is typically done when the focus is on the real number component of the complex number or when the context implies that the "i" is understood.

In this case, the answer choices are presented as single numbers (7, 5, -5), suggesting that the simplification has been applied. Therefore, the correct answer is A. 7i, which represents the sum of the imaginary parts without simplification.