Answer:
Geologists search rivers, mountains, and caves for clues about how and when the Earth was formed.
Explanation:
This would be an important idea to include in your summary because it contributes to the central idea of the entire passage. The passage is about the work of geologists, and this sentence/idea is the main idea.
The first sentence is correct.
Answer:
1. b. ship
2. c. journey
3. for 1. they sailed (only ships sail) and 2. they traveled/sailed to somewhere else, "they sailed in the Atlantic" to "visit new places." And that's usually called a journey
4. a.
