What property involves distributing a factor across a sum within parentheses?

The correct answer is the Distributive property because it specifically describes the operation of multiplying a single term by a sum or difference within parentheses. According to this property, you can distribute the factor outside the parentheses to each term inside the parentheses. For example, if you have a factor of 'a' multiplying the sum (b + c), you can express it as a(b + c) = ab + ac. This is fundamental in simplifying expressions and solving equations in algebra, as it allows for the expansion of expressions.

The other properties do not apply here. The Additive property typically refers to the idea that adding zero to a number leaves it unchanged. The Associative property deals with how numbers are grouped in addition or multiplication without changing the result, such as (a + b) + c = a + (b + c). The Commutative property focuses on the ability to change the order of numbers in addition or multiplication, as in a + b = b + a. These concepts are distinct from the function of distributing a multiplication factor across a sum, which is what the Distributive property addresses.