According to String Theory, Six Space-Time Dimensions Cannot Be Measured

According to string theory, six space-time dimensions cannot be measured except as quantum numbers of internal particle properties because they are curled up in size of the order of

A) 10−³⁵ m.
B) 10−¹⁵ m.
C) 10−¹⁰ m.
D) 10−⁸ m.
E) 10−³ m.