Select the most appropriate option to fill in the blank 4.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. thinking.
- In the context of the sentence, "thinking" is the most suitable term.
- It suggests that Wallace had been contemplating or pondering the same problems that Darwin was considering for his book.
- The other options ("dreaming," "saving," "searching") do not fit the context as well.