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

Options

A. 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

(a) and (b) can neither occur by themselves nor by initiation , (c ) can occur by itself , (d) occurson initiation.