选B,
因为where = in which,解释起来比较复杂,如下：
这句可以分成两个部分
1) Bungee jumping is an adventutous sport,popular with young adults.
2) courage matters more than strength in bungee jumping.
将两句合二为一,第二句中的bungee jumping用which替代后,多了一个 in：...young adults,which courage matters more than strength in.在英语中,一般习惯是将这个in 前置到引导词 which前面,变成：...young adults,in which courage matters more...
但选项中没有in which,由于 where = in which,因此选B.