Question

the engineering behind the knee - brace energy harvester works like other technologies to produce electricity from moving things. as the hiker walks along the trail, her knee straightens. this movement triggers mechanical gears in the brace to turn. a small generator converting the energy. collecting and storing the electricity. the hikers knee bending and straightening. using a battery to charge the hikers phone. to? choose the phrase that completes the sent triggers mechanical gears in the brace to turn.

Explanation:

The text describes that the movement of the hiker's knee (bending and straightening) is what initiates the turning of mechanical gears in the knee - brace energy harvester.

Answer:

The hiker's knee bending and straightening