All three answers would adequately solve your "flat basketball" problem, but the answer your teacher is probably looking for is a). When the air inside the basketball cooled off, the particles came closer together, causing the ball to deflate. If the air inside the ball was warmed back up, the particles would spread out more (the air would expand) and the ball would inflate again. Hope that helps!!
The cold made the particles clump to together so the answer could be a or b
To restore a soft basketball left in the cold, it's best to pump it up a little to increase the air pressure inside. This action leads to the air warming up and expanding, refilling the ball more efficiently. Alternatively, leaving it alone to warm up is a slower option.
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