Final answer:
The conjugate of the given complex number z = 3 + 4i is 3 - 4i.
Step-by-step explanation:
The conjugate of a complex number is obtained by changing the sign of its imaginary part.
In this case, the complex number is z = 3 + 4i. So, the conjugate of z is 3 - 4i.
Therefore, the correct answer is a. 3 - 4i.