B. The sum of three products; there are three terms.
We have been given an expression . We are asked to choose the sentence which best describes our given expression.
We can see that our given expression has three variables and each of them is multiplied by a number. Therefore, there are three terms is our given expression.
We can see that each term is product of a number and variable and all terms are being added, therefore, our expression represents the sum of three products and option B .