Answer:
the air molecules from the cookies diffused faster than the air molecules from the pumpkin
Step-by-step explanation:
The smell of cookies reaches first because the air molecules from the cookies were able to diffuse faster than the air molecules from the pumpkin.
At constant temperature, the diffusion rates of two molecules would be dependent on the size of the molecules. The bigger the size of the molecule, the more time it will take for the molecule to diffuse and vice versa.
Thus, since the pumpkin and the cookies were baked at the same temperature, the smell of the cookies was perceived first because the air molecules of the cookies are smaller in size than the air molecules of the pumpkin.