What is the main difference between steam engines and internal combustion engines?

Question

a) Steam engines do not use the combustion of fuel.

b)Pistons are found only in internal combustion engines.

c)In steam engines, combustion occures externally.

d)Internal combustion engines are larger.

Answer 1

c

Answer 2

c - that is why they are  called external combustion engines.

a - can not be right, the steam has to be made some where (even in the fire-less ones)

b - can not be right,  they both can have pistons (or turbines)

d- can not be right as steam engines on articulated engines were very large (not to mention the steam turbines found in power houses).