**Question:**

2,1, 2, 4, 4, 5, 6,7, 8, 8, 10, 11,(......)

**Option A):**

10**Option B):**

12**Option C):**

9**Option D):**

11

**Correct Answer is Option A):**

10

**Explanation:**

The given sequence is a combination of three series: (1). 1st, 4th, 7th, 10th, 13 terms 1, 4, 6, 8, (.....) (2). 2nd, 5th, 8th, 11th term 1,4,7,10, (.....) (3). 3rd, 6th, 9th, 12th terms i.e. 2, 5, 8, 11, (.....) Clearly, It consists of consecutive even numbers. So, the missing number is 10.