According to the passage, which of the interest of scuba diving is NOT  mentioned?

* Hướng dẫn giải

Dẫn chứng: At the moment, scuba diving has four main areas of interest: recreation purposes, commercial purposes, scientific research and military activity as well. The most frequent reason why people go for scuba diving is because they want to relax in a special way, by having contact with a less known world.