Which power source is listed as the primary power supply option for the device?

• A. AA alkaline
• B. USB-C power supply
• C. NiMH rechargeable pack
• D. 3.7V lithium polymer battery pack

Answer: (D)

The main idea is identifying the device’s built-in primary power source. The 3.7V lithium polymer battery pack is the best choice because it serves as the device’s internal, primary power source, providing high energy density in a compact, lightweight package—perfect for portable field equipment that must run without constant external power. Being rechargeable, it supports extended use across missions without frequent replacements.

Alkaline AA cells are bulky and need regular replacement in the field, which isn’t ideal for a rugged, mission-critical device. NiMH packs trade some energy density for reusability, but for the same form factor they’re heavier and offer less runtime than a LiPo pack. A USB-C power supply, while useful for charging or powering the device when plugged in, is not the built-in power source the device relies on during operation away from power sources. Thus, the LiPo pack best fulfills the role of the primary, internal power source.