Guillermo was finding it difficult to walk up the steps to his family’s apartment. His doctor thinks that his cells might not be getting enough oxygen or glucose Why does having low levels of glucose or oxygen in his cells make it difficult for Guillermo to walk up steps? (Sentence starter: It is difficult for Guillermo to walk up steps because...

Without enough oxygenated blood cells, his brain isn't getting enough oxygen, making it harder for his brain to process movement.

Explanation:

When you don't have enough oxygenated blood cells, you aren't getting enough oxygen to your brain, making it harder for you brain too process movement.

i believe it is-

d.) gravity pulled particles of dust and gas together to form planets.