The process of planet formation through collision and sticking of small celestial bodies is called:

Correct option is B

The correct answer is (b) Accretion
Explanation:
• Accretion involves gradual growth by collision and coalescence of planetesimals.
• Operates in protoplanetary disks during early Solar System formation.
Information Booster:
• Accretion theory proposed in mid-20th century astronomy.
• Planetesimals formed from dust and gas in solar nebula.
Additional Knowledge (Incorrect Options):
(a) Differentiation
• Refers to internal layering of planets.
• Occurs after planet formation.
(c) Fragmentation
• Involves breaking apart, not growth.
• Opposite of accretion process.
(d) Degassing
• Release of gases from planetary interior.
• Related to atmosphere formation, not planet formation.