X denotes the number of times heads that occur in n tosses of a fair coin. If $P(X=4), P(X=5)$ and $P(X=6)$ are in arithmetic progression, the largest value of n is

• A

  $7$
• Correct answer
  B

  $14$
• C

  $21$
• D

  $28$

Hence, the correct answer is option: 'B'.