A body is made of matter and matter is made of very small particles called molecules, which are constantly moving.
The molecules in a cold body move little but in a hot body they move more because we have provided heat.
When a hot body comes into contact with a cold body these things happen:
1) the hot body cools down (becomes cold).
2) the cold body heats up (gets hot).
3) both bodies reach the same temperature.
In summary, the heat passes from the hottest body to the coldest body until thermal balance is reached (the two bodies reach the same temperature).
If my letter guessing is right i would go with A or the first one
Answer: b. Muscles
A metazoa is a division of animal kingdom that includes all animals expect protozoa and sponges. Metazoa division includes multicelluar animals, which exhibit highly differentiated cells. They have muscular and nerve system and well coordinated tissues and organs. Locomotion requires a coordination activity of muscular, skeletal and neural system. It is mainly achieved by contraction and relaxation of muscles that occurs due to specialized muscle proteins named as actin and myosin which receives signals from nerves.
Hence, locomotion in metazoa is due to contraction of muscles.