Select the most appropriate option that can substitute the highlighted segment in the given sentence. If there is no need to substitute it, select ‘No substitution required’.
The purchase of computers is sure to cost more than you estimate.

Correct option is A

The correct substitution of the highlighted words is (a) No substitution required.
Explanation: The construction “be sure to + V1” expresses a strong expectation or certainty about a future action.
Here, “is sure to cost” is perfectly idiomatic and grammatically correct. Options (b), (c), and (d) misuse the pattern: “sure of + noun/gerund” typically states certainty about a thing/outcome, not about an action with an object like “cost more,” and “to costing” is ungrammatical after “sure to.”
Grammatical rule used:
· be sure to + base verb → certainty about an action (e.g., “is sure to rise”).
· be sure of + noun/gerund → certainty about something (e.g., “is sure of success / winning”).
· Example: The new policy is sure to increase applications this year.
· Information booster: Use “be sure of” before nouns/gerunds (“She is sure of winning.”), but choose “be sure to + V1” for actions (“She is sure to win.”).