Which types of brake systems are commonly found in vehicles?

The selection of disc brakes and drum brakes as the correct answer highlights the fundamental types of braking systems commonly used in vehicles. Disc brakes utilize a rotating disc and calipers, providing effective heat dissipation and improved stopping power, making them a preferred choice for modern vehicles, particularly in the front wheels. Drum brakes, on the other hand, employ a set of shoes that press against the inside of a rotating drum, offering simplicity and cost-effectiveness, which is why they are still prevalent in rear brake applications, especially in older or less expensive vehicles.

While the other options mention various brake system technologies, they do not directly categorize the primary systems used for stopping a vehicle. Anti-lock brakes are a safety feature that prevents wheel lockup during braking but do not refer to a distinct type of brake system. Similarly, parking brakes and electronic brakes serve specific functions but are not primary braking mechanisms for normal vehicle operation. Pneumatic brakes are generally more common in larger vehicles and heavy equipment, while mechanical brakes are more of an older technology, reflecting a different context in braking system design. Thus, focusing on disc and drum brakes accurately encapsulates the essential types of brake systems found in most passenger vehicles today.