The correct answer is: B. add on modules.
Arduino shields are add-on modules that can be plugged into an Arduino board to add new features and functionality. They are available for a wide range of purposes, such as motor control, wireless communication, and data logging.
Option A, “extra peripherals”, is incorrect because Arduino shields are not peripherals. Peripherals are devices that are connected to a computer or other electronic device, but they are not part of the main unit. Arduino shields, on the other hand, are part of the Arduino board.
Option C, “connectivity modules”, is incorrect because Arduino shields are not just for connectivity. They can be used for a wide range of purposes, as mentioned above.
Option D, “another Arduinos”, is incorrect because Arduino shields are not Arduino boards. They are add-on modules that can be plugged into an Arduino board.