Hold a mug upside down on top of water in a bucket. Try to push it as is, into the water. It takes a lot of effort to do that. Now tilt the mug a little, so that bubbles come out, the mug goes down easily. This proves that mug had air in it and that:

• A. Air occupies space
• B. Bubbles help in sinking
• C. We cannot sink when we are upside down in an empty boat
• D. Nothing