Question

2+4i define as complex noncomplex real or pure imaginary

Answer 1

This is a complex number.

It has a real part (2) and an imaginary part (4).

A complex number is of the form $a+bi$, where a is the real part, and b is the imaginary part.

In reality, there's no such thing as a pure imaginary number; rather, it is a complex number with a real part equal to 0, but use the naming conventions your instructor recommends.