3908i is a pure imaginary number. So option B is coorect
Solution:
Given that, a number is 3908i
We have to find the type of number which it belongs to from the given set of options
If we observe the number clearly, we can see the “i” behind the number 3908, where “i” value is square root of ( - 1 ).
We know that, “i” is not real, so 3908i is also not real.
And it has other operation like a + bi or a – bi
So, it is just imaginary number but not a complex number.
Hence, the given number is pure imaginary number. So option b is correct.