Final answer:
The greatest common factor of the expression $3a² - 9$ is 3, which corresponds to Option A: $3a$.
Step-by-step explanation:
To find the greatest common factor (GCF) of the expression $3a² - 9$, first, notice that each term in the expression is divisible by 3. Factoring out the 3, the expression becomes 3(a² - 3). However, this is not completely factored since a² - 3 does not have any common factors with 3, and it cannot be factored further. Hence, the greatest common factor of $3a² - 9$ is simply $3$, which corresponds to Option A: $3a$.However, when it comes to a triangle with all sides of odd length, this becomes impossible. The square of an odd number is always odd, and the sum of two odd numbers is always even. Hence, if both a and b are odd (producing odd squares), their sum a² + b² would be even, and cannot equal the square of another odd number (c²). Therefore, the answer is false; right triangles with all sides being odd integers cannot exist because it would violate the Pythagorean theorem.