Which expression simplifies to a complex number in the form \( \mathrm{a}+\mathrm{bi} \) where b is not equal to 0 ? \( \begin{array}{l}\text { A. } 3(3-4 i) \\ \text { B. }(3 i)(4 i) \\ \text { C. }(3-4 i)+(3+4 i) \\ \text { D. }(4+3 i)-(5+3 i)\end{array} \)

Let's simplify each expression and see which one yields a complex number in the form \( a + bi \) where \( b \neq 0 \). A: \( 3(3-4i) = 9 - 12i \) (This gives \( b = -12 \), so this option qualifies.) B: \( (3i)(4i) = 12(i^2) = 12(-1) = -12 \) (This is a real number, \( b = 0 \).) C: \( (3-4i) + (3+4i) = 3 - 4i + 3 + 4i = 6 + 0i \) (This is also a real number, \( b = 0 \).) D: \( (4+3i) - (5+3i) = 4 + 3i - 5 - 3i = -1 + 0i \) (This is again a real number, \( b = 0 \).) The only expression that simplifies to \( a + bi \) with \( b \neq 0 \) is: **Answer: A.**