The multiplication of two complex conjugates can be expressed as follows: if we have two complex numbers \(a + bi\) and \(a - bi\), their product will be:
\[
(a + bi)(a - bi) = a^2 - (bi)^2 = a^2 - b^2(-1) = a^2 + b^2
\]
The result is always a real number since it is the sum of the squares of the real and imaginary parts.
Now let's analyze the options you provided:
1. **20** - This is a real number and can be a result of multiplying two complex conjugates.
2. **25 + 4i** - This has an imaginary part (4i) and thus cannot be the result of two complex conjugates being multiplied since the result must be real.
3. **16i** - This is purely imaginary and cannot be the result either.
4. **9 - 9i** - This has an imaginary part (-9i) and also cannot be the result.
Based on this analysis, the only feasible result from the options provided that could come from multiplying two complex conjugates is **20**.