Answer:
B. The walker will not get tired as fast.
Step-by-step explanation:
Based on the given passage, it is narrated that new electric backpacks which could be used as generating sets to power up electrical appliances were available and the up and down movement of the backpack acted as the generator.
From paragraph 4 of the given passage, it is said that the up and down motion reduces the weight of the pack.
Therefore, the detail that should be added to it is that the walker will not get tired as fast.