a)
WATER: kite surfing, white-water rafting/canoeing, cliff diving, jet skiing, windsurfing, sailing, scuba diving
LAND: rollerblading, archery, free running (parkour), snooker, ice climbing, mountain biking, weightlifting, skateboarding, sand boarding, ice hockey, snowboarding, ice skating, motocross, indoor climbing, storm chasing
AIR: BASE jumping, kite surfing, cliff diving, paragliding, bungee jumping, ski jumping
b)
Not extreme sports: rollerblading, archery, snooker, weightlifting, skateboarding, ice hockey, sailing, ice skating and indoor climbing are not extreme sports.
Water: water polo, synchronised swimming, kayaking
Land: downhill skating, rugby, lacrosse
Air: skydiving, hang gliding