Question

1. if the respiratory system cannot bring in enough oxygen, which system is directly affected?

digestive system
circulatory system
skeletal system
excretory system

Explanation:

The respiratory system's main function is to take in oxygen. The circulatory system (specifically, the blood in the cardiovascular part) is responsible for transporting oxygen throughout the body. If the respiratory system fails to bring in enough oxygen, the circulatory system, which relies on that oxygen to be transported (e.g., oxygen binds to hemoglobin in red blood cells for circulation), is directly affected. The digestive system deals with food breakdown, the skeletal system with support/protection, and the excretory system with waste removal - none of these have the direct oxygen - transport relationship like the circulatory system does with the respiratory system.

Answer:

Circulatory system