Teacher:In this task, you will be shown a passage. You need to write a fill-in-the-gap question based on your understanding of the events that might be inferred from the passage. Your question should be answerable based on the passage and only have one correct answer. Show the gap in your question with a _ .
Teacher: Now, understand the problem? Solve this instance: Some of the world's most famous landmarks and monuments were plunged into darkness this evening to raise awareness of climate change. Big Ben and the London Eye switched off their lights for Earth Hour, joining the Eiffel Tower, Brandenburg Gate in Berlin and St Basil's Cathedral in Moscow. The annual event, organised by conservation organisation WWF, saw more than 700 iconic landmarks worldwide go dark at 8.30pm local time, as millions of homes turned off their power. Scroll down for video Big Ben switched off its lights for an hour from 8.30pm to mark Earth Hour, an annual event to highlight the effects of climate changeSome of Britain's most iconic landmarks were plunged into darkness to raise awareness of climate changeLights at Big Ben, Buckingham Palace, Tower Bridge and Old Trafford switched off for Earth Hour at 8.30pm700 monuments worldwide went dark, including the Eiffel Tower in Paris and Brandenburg Gate in Berlin
Student:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
'WWF works hard to address many of the environmental issues we face on our planet but _ is a chance for everyone to show that they care and are willing to do their bit to help because collective action has never been more vital.