In following number series, two terms have been put within brackets. Choose the appropriate option - Look at this series: 2, 4, 6, 8, 10, . . . What number should come next ?

Answer: B. 12

This is a simple addition series.
Each number increases by 2.
Like -
First number is 2
Second number = 2 + 2 =4
Third number = 4 + 2 = 6
Fourth number = 6 + 2 = 8
Fifth number = 8 + 2 = 10  and
Sixth number = 10 + 2 = 12
Hence, The answer is (b) 12.