Answer: C. 4+9i
Explanation:
A combination of a real and an imaginary number is called complex number.
Since, - 7 is the negative integer and an integer is always the real number only therefore it can not be the complex number,
2+√3 is the irrational number which is only a real number therefore, it can not be the complex number,
In number 4+9i, 4 is the real number and 9i is the imaginary number, Therefore it is a complex number,
π is the irrational number and an irrational number is always a real number therefore it can be the complex number.
Thus, Option C is correct.