Complete the sentences with the correct prefixes. The team attacked but couldn’t score a goal. Then, through a/an ordinary piece of good fortune, the other team accidentally kicked the ball into the wrong goal.
The correct answer here is extra. Then, through an extraordinary piece of good fortune, the other team... The prefix extra is used to show a greater degree of something; so this piece of good fortune wasn't something that happens all the time - it is rather very strange and unusual, which is explained through extraordinary.