Which of the following expansion slots would be MOST commonly used to add peripheral devices onto laptops?

SD Card slots are used for flash memory storage media and are not a general-purpose peripheral expansion interface.

PCMCIA (Personal Computer Memory Card International Association), also known as PC Card, is a hardware standard specifically designed for the laptop form factor to allow expansion of functionality through hot-swappable cards. It enables adding peripherals such as modems, network adapters, storage controllers, and wireless cards to laptops without opening the chassis. PCMCIA was the dominant laptop expansion interface before being succeeded by ExpressCard.

DIMM is a desktop memory module slot form factor and is not used for adding peripheral devices - it is strictly for RAM installation.

SODIMM is the laptop equivalent of DIMM and is used exclusively for RAM installation, not for connecting peripheral devices.