If a learner is able to perform the four basic operations on whole numbers, fractions and decimal numbers, the learner is at:

Correct option is D

A learner who is able to perform the four basic operations (addition, subtraction, multiplication, and division) on whole numbers, fractions, and decimal numbers is in the Operating phase. This phase involves the ability to apply operations systematically and accurately across various numerical types.
Hence, the correct answer is (d) Operating phase.
Information Booster:
1. Operating phase: This is where students demonstrate proficiency in performing mathematical operations across different types of numbers.
2. Quantifying phase: Typically involves understanding and measuring quantities.
3. Partitioning phase: Refers to dividing or breaking down numbers or objects into parts.
4. Factoring phase: Involves recognizing and working with factors of numbers.
Additional Information:
· The Operating phase is essential for solving a wide range of mathematical problems, as it builds upon a foundation of understanding different numerical systems and applying the operations to them effectively.
· Mastery in this phase allows students to progress toward more complex mathematical tasks like algebra and advanced problem-solving.