The correct answer is: C. Return a formula result.
A worksheet formula is an expression that calculates a value. It can contain numbers, cell references, operators, and functions. The formula result is the value that is calculated by the formula.
Option A is incorrect because not all worksheet formulas manipulate values. For example, the formula =A1+A2 does not manipulate any values. It simply returns the sum of the values in cells A1 and A2.
Option B is incorrect because not all worksheet formulas manipulate labels. For example, the formula =A1+A2 does not manipulate any labels. It simply returns the sum of the values in cells A1 and A2.
Option D is incorrect because not all worksheet formulas use the addition operator. For example, the formula =A1*A2 does not use the addition operator. It simply returns the product of the values in cells A1 and A2.