In mammals, the powerful muscle that aids in breathing is the diaphragm. This muscle expands and contracts the chest cavity and forces air in and out of the lungs.
Hope that helped =)
Mass is anything you can touch
And mass is measured in kilograms or grams usually
If the scientists are studying the effects of different temperatures on the processing speed of a computer chip then they would need to know the temperature inside the computer.
However, your questions doesn't include the full question text, so I cannot be sure what answer you need.
If the question is what do they need to know to do this, the answer is C.
If the question is how could they measure this when they subject the computer to different temperatures, then the answer is D.
