Yesterday, our class had a discussion about     1     (ocean exploration ).

The majority of students are in favor of ocean exploration. In their opinion, through ocean exploration, we can     2     (know, environment ) to better understand environmental changes. What’s more,     3     (resource), which help deal with energy shortages. However, a small number of students     4     (different). They think human activities may not only cause severe ocean pollution, but also destroy biodiversity.

In my opinion,     5     (worthwhile, invest) moderate ocean exploration and we’d better not explore it     6     (cost, destroy, balance).