The very cold (about 20 K), dense clouds of gas thought to be the most massive objects in the Galaxy are called molecular clouds.
Answer: Option B
Step-by-step explanation:
Molecular clouds are basically the interstellar clouds made of dust and gaseous clumps. The clouds have an average density of 100 to 300 mcc with a temperature range of 10 to 20 K. The formation of stars takes place in the inner region of clouds. The size of molecular clouds may range from a few Light years to 600 Light years. A dar Nebula is the densest version of the molecular clouds.