ANSWER : B

Explanation :

Range of real constants is -3.4x10³⁸    to    +3.4x10³⁸ .

In exponential form it is -3.4E38    to    3.4E38

or -34E37    to    34E37

Notes :

Exponential form is also used in calculators etc.

For example:    3.94E2

Here "3.94" is known as "Mantissa" and "2" is known as "Exponent".