Complete the sentences by choosing a, b or c. 1 Coral reefs are ............ a islands. b towns. c ocean communities. 2 Coral is ............ a hard. b soft. c blue. 3 Coral polyps are ............ a huge plants. b sensitive creatures. c bright-coloured algae. 4 Coral reefs die because ............ a algae lose their colour. b people fish them. c the oceans' temperature increases.