C. Have you ever   27   World Oceans Day (WOD)? Theidea for WOD came from a meeting at the United Nations in1992.
     Ocean covers 70% of our planet. They were once cleanand beautiful, but now they   28   in serious trouble.Garbage, oil spills, and overfishing have made the number ofocean fish and plants   29   lower than before. If we don'tbeat the clock and fix the problem, a lot of sea life   30   soon.   31   the world's oceans, people clean up the beacheson that day. After all, we only have one Earth.
【題組】27.
(A) heard of
(B) heard from
(C) listened to
(D) sounded