Select the most appropriate option to fill in blank number 1.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. aspects.
The passage discusses different states (sleeping, dreaming, and waking) as important aspects of human life, suggesting that these are different features or dimensions of human experience.
The other options, such as "problems," "methods," and "angles," do not fit contextually as well as "aspects," which refers to different elements or facets of something.