Justin couldn’t understand why his friend had refused to work in a company that offered him a huge salary.
If it had been him in his friend’s place, he would definitely accepted such an offer.

The given sentence follows the conditional type 3 sentence structure. Conditional sentences are given as: If + (conditional clause) , (main clause)

In the case of a type 3 conditional sentence, the conditional clause is in past perfect tense (subject + had + V3), while the main clause follows a perfect conditional or perfect continuous conditional (would have + V3); where V3 is the past participle form of the verb. 

In the given sentence: ...If it had been him in his friend’s place, he would definitely accepted such an offer. "

The clause "...If it had been him in his friend’s place" is the conditional, and hence the main clause should be he WOULD HAVE DEFINITELY ACCEPTED such an offer.

The correct answer is therefore option B.