Select the most appropriate option to fill in the blank.
He insisted _________ paying the bill.

Correct option is B

The correct option to fill in the blank is (b) on.
Explanation: The verb insist collocates with the preposition on and is followed by a gerund (-ing form) when an action is insisted upon: insist on + V-ing. Hence, “insisted on paying” is correct. (Hindi: insist on = ज़ोर देना/अड़ जाना).
Example: He insisted on paying for everyone’s dinner.
Why other options are incorrect:
• (a) at — Used for location/time; not part of the idiomatic pattern ( insist at ✗).
• (c) by — Means “through the means of”; not used with insist ( insist by ✗).
• (d) for — Expresses purpose/benefit; not the collocation ( insist for ✗).
Information booster:
· Insist on + noun/gerund: She insisted on silence / coming early.
· With that-clause, use (should) + base verb or a declarative: He insisted that she (should) apologize.