Factorise Completely: 6ab - 3ac A. 3a(2b - c) B. 3(2ab - ac) C. ca(6b - 3c) D. 6a(b - c)

The terms are $6ab$ and $-3ac$.

The coefficients are 6 and 3. The GCF of 6 and 3 is 3.

Both terms contain the variable $a$.
The first term has $b$, but the second term does not.
The second term has $c$, but the first term does not.
So, the common variable factor is $a$.

The GCF of $6ab$ and $3ac$ is $3a$.

For the first term: $\frac{6ab}{3a} = 2b$
For the second term: $\frac{-3ac}{3a} = -c$

Comparing this result with the given options:
A. $3a(2b-c)$
B. $3(2ab-ac)$
C. $ca(6b-3c)$
D. $6a(b-c)$

The correct option is A.

The final answer is $\boxed{\text{A. } 3a(2b-c)}$.