Select the most appropriate option to fill in blank number 4.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. refers.
"Refers" means to mention, relate to, or indicate something.
In the passage, "the solar or sunspot cycle refers to this" means that the sunspot cycle is being identified as the phenomenon being described.
Meaning of the other options:
Pass: To move or go through something.
Cite: To quote or refer to a source.
Entrust: To assign responsibility to someone.
Hence, the chosen option is correct.