Clouds of butterflies have been sighted in southern Britain this summer, and wildlife lovers are being urged to help scientifically assess whether this species of insects are really increasing by joining the world’s largest butterfly survey.The Big Butterfly Count begins on Friday with reports of an unusually good year for butterflies. But ecologists warn this could be a mistaken perception, and 2017 is simply a modest improvement on last summer.The total abundance of common butterfly species has fallen by a quarter since monitoring began in 1976, with drastic declines for many once-familiar butterflies. Recent research has also revealed pronounced declines in urban butterflies over the past 20 years. David, the president of Butterfly Conservation, said, “Worryingly, we are now seeing the fortunes of some of our once common butterflies mirror those of our rarest species. And they too are now suffering significant declines, with butterflies declining more rapidly in urban areas than in the countryside.1.What are the wildlife lovers being urged to do?A) Go sightseeing in southern Britain.B) Do a scientific wild-animal survey.C) Check whether butterflies are increasing.D) Assess the decline of common butterflies.2.What does David say about butterflies?A) There are more butterflies in the city.B) Common butterflies also decrease sharply.C) The rarest species increase a little this year.D) Butterflies decrease faster in the countryside.