Explanation:

The Arithmetic Logic Unit (ALU) is a fundamental digital circuit within the CPU that performs both arithmetic and logical operations. Specifically, it is responsible for arithmetic operations like addition, subtraction, multiplication, and division, as described in option (b). Additionally, the ALU handles logical operations, which involve comparing data (e.g., equal to, greater than, less than), as described in option (c). Therefore, option (d) correctly states that the ALU performs both calculations (arithmetic operations) and logical comparisons, encompassing the full scope of its primary functions within the CPU. Options (a), (b), and (c) alone are incomplete descriptions of the ALU's capabilities.