Given,

17.99²-14.05²+(2343.75+81.55)÷?

It can be approximated as

(18)²-(14)²+(2343.75+80)÷?=230

= 324-196+2430÷?=230

= 2430÷?=230-130

= 2430÷100

=24.3 ≈ 24

Hence, Option C i correct.