Which factor is critical for ensuring that fries are adequately cooked?

Crispiness on the outside is a crucial factor in ensuring that fries are adequately cooked. When fries achieve a crispy exterior, it indicates that they have been exposed to the proper cooking temperature for the right amount of time. This outer texture is essential because it contributes to the overall taste and mouthfeel, enhancing the dining experience. It also signifies that moisture is locked inside, preventing the fries from becoming soggy, which could indicate undercooking.

On the other hand, the other options represent characteristics that do not necessarily ensure proper cooking. For instance, while a bright yellow color may be desirable and indicate that the fries have been cooked sufficiently, it is not an absolute indicator of doneness as different potatoes can yield different shades even when cooked properly. Feeling hot to the touch is also not a definitive measure of doneness; fries may be hot without being adequately cooked through or crispy. Lastly, fries that are dull and limp suggest undercooking or improper frying techniques, which is the least desirable outcome for quality fries.