In a double, where two constrictions are available, improved cylinder and modified are a good pairing, especially in fixed-choke guns. If screw-in chokes are an option, try a more forgiving match, like skeet and light modified. Shoot the more open barrel first on the covey rise, then the tighter barrel as the birds make their escape.
The CD and DVD have a single track of data in the form of a spiral, which starts as the center going outwards. The data is stored on the bumps or pits which are then read by the CD/DVD layer. The bumps/pits on a DVD are much smaller than on CD, allowing the DVD to store more data.
In brief, CD (Compact Disc) is primarily used for delivery of music, DVD (Digital Versatile Disc) primarily for standard definition (720x480 in the North America, 720x576 in most of the rest of the world) video, and Blu-ray Disc primarily for high definition (1920x1080) video.