Final answer:
Tin is the metallic element used for coating the inside of cans, providing a non-toxic and corrosion-resistant layer to protect the steel, which makes up the main body of the can.
Step-by-step explanation:
The metallic element that is used as a corrosion-resistant coating on the inside of cans used for packaging food, oil, and other substances is tin (option a). Tin is employed in the manufacture of tinplate, which is essentially steel coated with a thin layer of tin. This tin coating provides a corrosion-resistant barrier that protects the steel from rusting. While zinc is also used to protect metals from corrosion and is found in galvanized steel, tin is the more common choice for coating the inside of food and substance containers. This is partly because tin is non-toxic and resists corrosion from the contents of the cans. In contrast, lead (option d), which is used in lead-acid batteries, is not suitable for contact with food due to its toxicity. Aluminum (option c) cans also feature protective layers, but they often include a thin plastic liner in addition to the metal itself. It is important to note that despite being called 'tin cans', modern containers are typically made from steel with a tin coating and not purely from tin.