When you breathe the first step is that your lungs expand. why is this step needed

When you breathe in, or inhale, your diaphragm contracts and moves downward. This increases the space in your chest cavity, and your lungs expand into it. The muscles between your ribs also help enlarge the chest cavity. They contract to pull your rib cage both upward and outward when you inhale.

Explanation:

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answer:

technetium is the most reactive. this is followed by silver. the least reactive out of these three elements is strontium.