Which is the best explanation for what has occurred? The runner's muscles have accumulated lactic acid.
The runner’s body has failed to perform cellular respiration.
The runner’s cells are relying completely on aerobic respiration.
The runner’s muscles have accumulated carbon dioxide.

when you breathe in, or inhale, your diaphragm contracts (tightens) and moves downward. this increases the space in your chest cavity, into which your lungs expand. the intercostal muscles between your ribs also enlarge the chest cavity. they contract to pull your rib cage both upward and outward when you inhale.

to figure the total magnification of an image that you are viewing through the microscope is really quite simple. to get the total magnification take the power of the objective (4x, 10x, 40x) and multiply by the power of the eyepiece, (usually 10x)