Explanation:

- Finding factors: We need to find the greatest common factor (GCF) of 120, 360, and 210.

- Factors of 120: 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 24, 30, 40, 60, 120

- Factors of 360: 1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 18, 20, 24, 30, 36, 40, 45, 60, 72, 90, 120, 180, 360

- Factors of 210: 1, 2, 3, 5, 6, 7, 10, 14, 15, 21, 30, 35, 42, 70, 105, 210

- Common factors: The common factors of these numbers are 1, 2, 3, 5, 6, 10, and 15, 30.

- Out of these, the highest common factor is 30.

- Options:

- Option 1: 12 - Not the highest common factor.

- Option 2: 30 - Correct answer.

- Option 3: 3 - Not the highest common factor.

- Option 4: 15 - Not the highest common factor.