READING: Read and complete each numbered blank in the passage with the correct answer A, B, C, or D

Coral reef facts
When you look at a coral reef, you might think that you are seeing a group of colourful rocks. But corals are actually ___(1)___ creatures. Coral reefs mostly grow in shallow, clean ocean waters on either side of the Equator, because they need sunlight and warm temperatures to survive. The Great Barrier Reef is the ___(2)___ reef system on Earth. You can even see it from space!
Lots of sea creatures call coral reefs their ___(3)___ such as giant clams, sea turtles, and cuttlefish. The reefs provide them with everything they need, including food and shelter. Plants also live on reefs. For example, algae live inside soft coral, using sunlight to provide food and help the coral grow. ___(4)___, coral reefs are endangered. The biggest threats to them are pollution from oil spills, damage from ships and boats, and climate change, ___(5)___ makes the water warmer and more acidic. Many people are working hard to clean up the pollution on land and in the sea to save coral reefs.
(Adapted from: https://www.natgeokids.com)