What is the key advantage of using human-motion-powered devices over solar-powered devices during a nighttime rescue operation?

They are always lighter and easier for rescue workers to carry.

They produce a much higher voltage output for powerful equipment.

They do not require sunlight and can function continuously in the dark.

They can store captured energy for a much longer duration than solar batteries.

A company is developing an emergency locator beacon for hikers. To ensure it works even if the main battery is depleted, which feature would utilize the principle of human kinetic energy?

A secondary, single-use chemical battery.

A hand-crank to manually generate power for a signal.

A highly insulated case to preserve battery life in the cold.

An integrated solar panel for charging in direct sunlight.

The user's physical fitness level.

The amount of chemical energy stored in the body.

External environmental conditions like weather or time of day.

The efficiency of the energy harvesting device.