18. let z = a + bi represent a general complex number. as noted in the lesson, the conjugate of z, abbreviated conj(z) or conj(a + bi) is the complex number a-bi. also, the modulus of z, modulus(z) is the "size" of z, or √(a2 + b2). which of the following is true for all complex numbers? a) all of the following b) z*conj(z) = [modulus(z)]2 c) z + conj(z) = 2a d) z - conj(z) = 2bi e) none of the above 19. using the definition of "size" of z from problem #18, which of the following is largest? a) 3i b) -7 c) 4 d) -2i e) 4 + 4i f) none of the above