Why are the 1300 nm and 1550 nm regions of the fiber spectrum primarily used for optical communications?（）

• A、They are both regions of lowest loss.
• B、They are both regions of low reflections.
• C、They are both regions of low index of refraction.
• D、They are both regions of low chromatic dispersion.
• E、They are both regions of low Polarization Mode Dispersion (PMD).