Q2:Pole vaulter Sergei Bubka claimed the championship title in the 1988 Olympic Games.In the IAAF World Championships he got even better results.How many championships did he win in IAAF competitions?

• 问:撑杆跳著名选手布勃卡在1988年奥运会上夺冠，但在田径世锦赛上他取得了更加骄人的成绩，请问他共获得过多少次田径世锦赛冠军？