Step 1: Understanding the term "Petrology".
Petrology is the branch of geology that studies rocks, their origin, composition, and structure. It is concerned with understanding how rocks form, their mineral composition, and their role in the Earth's processes.
Step 2: Evaluating the options.
- (A) Petrology: Correct. Petrology is the study of rocks and their properties.
- (B) Oceanography: Incorrect. Oceanography is the study of the Earth's oceans and seas, including their physical properties and biological aspects.
- (C) Palaeontology: Incorrect. Palaeontology is the study of fossils and ancient life forms, not rocks.
- (D) Hydrology: Incorrect. Hydrology is the study of water on Earth, its distribution, and its movement.
Step 3: Conclusion.
Petrology is the correct field of study when it comes to rocks.
Final Answer: (A) Petrology.