Alternating current is commonly used in which of the following places?

Alternating current (AC) is widely used in homes because it is efficient for transmitting electricity over long distances. The electrical grid supplies homes with AC power, which is favored due to its ability to easily change voltage levels using transformers. This capability allows for the transmission of electricity over vast distances with minimal loss of energy. In residential settings, appliances and devices are designed to operate efficiently on AC, making it the standard form of electricity supplied to homes.

Other environments, such as cell phones and airplanes, primarily use direct current (DC). Cell phones operate on batteries, which supply DC power, and many airplane systems are designed to work with DC as well. Ships also have variations in their power systems often balanced between AC and DC, primarily for specialized operations, but typically, most of their main electrical systems will be AC.

Thus, homes stand out as the most common places where alternating current is utilized, making this the correct answer for the question.