1 . x=a2-7a+6,y=a2-2a+1,z=a2-5a+4

• A. $\left(a-4\right)$
• B. $\left(a-1\right)$
• C. $\left(a-6\right)$
• D. ${\left(a-1\right)}^2$

Answer: Option B

Explanation: