The spontaneity means having the potential to proceed without assistance of external agency. The processes which occur spontaneously are

Options

A. flow of heat from colder to warmer body
B. gas in a container contracting into one corner
C. gas expanding to fill the available volume
D. burning carbon in oxygen to give carbon dioxide

Answer

C, D

Explanation

Gas expands or diffuse in availabe space spontaneousl, e.g., leakage of cooking gas gives smell of ethyl mercaption spontaneously. Moreover, burning of carbon to `CO_(2)` is also spontaneous