Final answer:
The multiplicative inverse of −18 is the number that, when multiplied by −18, results in 1, which is −1/18.
Step-by-step explanation:
The multiplicative inverse of a number is defined as a number which, when multiplied by the original number, results in 1. For the number −18, its multiplicative inverse is the number that when −18 is multiplied by it, the result is 1. To find this, we consider what number multiplied by −18 gives 1. The answer is −1/18, which means the multiplicative inverse of −18 is −1/18.
Therefore, the correct answer to what is the multiplicative inverse of −18 is:
A) −1/18.