Select the most appropriate option to fill in blank number 1.
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. in.
The phrase "in diameter" is a standard way of expressing the measurement of a circular object’s width.
The structure "[measurement] in diameter" is commonly used in scientific and mathematical contexts.
Meaning of the other options:
On: Refers to a position atop a surface.
At: Specifies a specific point or location.
Of: used to indicate belonging, relation, or composition.
Hence, the chosen option is correct.