A. [digits][.digits][(E|e)[(+|-)]digits].
B. [digits][+digits][(E|e)[(+|-)]digits].
C. [digits][(E|e)[(+|-)]digits].
D. [.digits][digits][(E|e)[(+|-)]digits].
Floating-point literals may also be represented using exponential notation: a real number followed by the letter e (or E), followed by an optional plus or minus sign, followed by an integer exponent. This notation represents the real number multiplied by 10 to the power of the exponent.