Definition: You are given a paragraph, a question and some answer options (associated with "A", "B", "C", "D", etc.) You need to list all the correct answer options with their associated letters (e.g. "A" can be a valid answer). Note that sometimes, more than one option can answer the question correctly and completely. In those cases, please generate all such options separated by a comma (e.g. "A, B" is a valid answer). Do not generate anything else apart from one or more of the following characters: 'A', 'B, 'C', 'D', etc.
Input: Paragraph- Sent 1: Earth processes have not changed over time.
Sent 2: The way things happen now is the same way things happened in the past.
Sent 3: Mountains grow and mountains slowly wear away.
Sent 4: The same process is at work the same as it was billions of years ago.
Sent 5: As the environment changes, living creatures adapt.
Sent 6: They change over time.
Sent 7: Some organisms may not be able to adapt.
Sent 8: They become extinct.
Sent 9: Becoming extinct means they die out completely.
Sent 10: Some geologists study the history of the Earth.
Sent 11: They want to learn about Earths past.
Sent 12: They use clues from rocks and fossils.
Sent 13: They use these clues to make sense of events.
Sent 14: The goal is to place things in the order they happened.
Sent 15: They also want to know how long it took for those events to happen. 
Question: Who wants to learn about Earth's past? (A) Some organisms (B) Geologists (C) Doctors (D) Musicians.
Output:
B.