Final answer:
The width of the dining room can be determined by the term 12ab in the given function.
Step-by-step explanation:
The area of the dining room is given by the function 9a^2 + 12ab + 4b^2. To find the width of the room, we need to isolate the term that represents the width. Let's examine the function:
9a^2 + 12ab + 4b^2
The only term that contains 'b' is 12ab, so this represents the width of the room. Therefore, the width of the room is 12ab.
Therefore, the correct answer is b) The width of the room is 12ab.