The New Zealanders Dwayne van der Sluis and Andrew Akers must be the happiest people on Earth now that their (1) ... and latest craze, zorbing, has become a success. Zorbing involves standing in a ball  — or zorb  — which consists of specially hardened plastic. The zorb is rolled down a hill, speeding at about 50 kilometres an hour. It may sound like quite a (2) ... pastime, but the 70 centimetres of air between you and the ground make it (3) ... to get hurt. That's why zorbing didn't take long to gain in (4) ... .