Find the greatest common factor of 4 and 12 using prime factorization.

The correct option is D 4
Expanded form of 4 with prime factors = $\underset{–}{2}\times \underset{–}{2}$
Expanded form of 12 with prime factors = $\underset{–}{2}\times \underset{–}{2}\times 3$
Product of common factors = $2\times 2$
Hence, GCD = $4$