Final answer:
T-shirts and shorts that are bought together by Steve would be classified as complementary goods because their usage enhances one another.
Step-by-step explanation:
If Steve tends to buy t-shirts and shorts together, these items would be considered complementary goods. Complementary goods are items that are often used together, such that the consumption of one good enhances the consumption of the other. This concept is in contrast to substitute goods, which can replace each other in use, and is different from normal goods, which are products whose demand increases as income increases.
Giffen goods are a rarer case where an increase in price leads to an increase in the quantity consumed because the good is so essential that the consumer reallocates their budget to buy more of that good despite its increased cost. In Steve's situation, t-shirts and shorts are typically worn as an outfit, hence buying one often increases the likelihood of buying the other, making them a classic example of complementary goods.