In following number series, two terms have been put within brackets. Choose the appropriate option

Look at this series: 7, 10, 8, 11, 9, 12, . . . What number should come next?

** Option:**

**A.**7

**B.**10

**C.**12

**D.**13

**Answer: B . 10**

** Justification:**

This is a simple alternating addition and subtraction series.

In the first pattern, 3 is added;

In the second pattern, 2 is subtracted.

Rule =(1st number) (1st number + 3 = 2nd number) (2nd number - 2 = 3rd number) (3rd number + 3 = 4th number)

Now (7) (7 + 3 = 10) (10 - 2 = 8) (8 + 3 = 11) (11 - 2 = 9) (9 + 3 = 12) (12 - 2 = 10)...

So the answer is **b = 10.**