A hot "bubble" of air that breaks away from the warm surface and rises, expanding and cooling as it ascends, is known as a(n) . a. low pressure riser b. hot mass c. orographic uplift d. thermal

Thermal

Explanation: All areas on the earth surface does not absorb equal amount of sunlight, as a result of this, some areas tend to heat up more quickly than the others. The air in contact with these heated areas becomes  warmer than its surroundings causing a hot bubble of air called ''thermal'' to break away from the  warm surface,rising, expanding and cooling as it ascends, as observed during cloud development.