Final answer:
Russet potatoes (option a) are the best choice for making French fries because their starchy composition leads to a crispy exterior and a fluffy interior after frying.
Step-by-step explanation:
The best type of potato for making French fries is the russet potato. This is because russet potatoes are classified as 'starchy' potatoes, containing mostly unbranched polymers of glucose. This composition makes them ideal for frying as they become crispy on the outside while remaining fluffy inside, which is the desired texture for French fries.
Other varieties, such as waxy potatoes or sweet potatoes, have different starch compositions that result in different textures when cooked. Waxy potatoes, like new red potatoes, tend to maintain their shape and firmness better after cooking, which is not ideal for French fries, while sweet potatoes have a different flavor and sweetness level that deviates from the classic French fry taste.