**A**

Answer: A. 2

Solution:

The greatest common factor of two or more numbers is the highest factor that can be used in dividing all the numbers.

E1 = 4k = 2×2×k

E2 = 18k4 = 2 × 3 × 3 × k × k × k × k

E3 = 12 = 2×2×3

The number or expression they all have in common is 2.

This makes 2 the greatest common factor.

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