Câu hỏi:

Read the passage and choose the best answer

Africa's wild giraffe population has plunged dramatically and the world's tallest animals are in the process of a "silent extinction", a conservation group has reported. Giraffe populations have fallen by up to 40% over the last 30 years, the International Union for Conservation of Nature says in the latest edition of its "Red List" of endangered species. The gentle giants' numbers have dipped from as many as 163,000 in 1985 to just over 97,000 in 2015, according to the report. The steep decline was one of the headline statistics from the report, and is driven by some familiar factors including habitat loss, civil unrest and unforgettably, illegal hunting. Elsewhere, of the 742 newly recognized bird species in the list, 11% are considered threatened - and 13 already listed as "extinct". Many species are slipping away before we can even describe them. This IUCN Red List update shows that the scale of the global extinction crisis may be even greater than we thought. Among bird species under threat is the African grey parrot, a popular pet, which is now classed as "Endangered" on the list because of "unsustainable trapping and habitat loss." Across animals, birds, insects, aquatic life and plants, the IUCN Red List now includes 85,604 species, of which 24,307 are threatened with extinction. The plunge in the number of wild giraffe prompted the group to move the animals from the "least concern" rating to "vulnerable", in the report. "While giraffes are commonly seen on safari, in the media and in zoos, people – including conservationists - are unaware that these majestic animals are undergoing a silent extinction," IUCN co-Chairman Julian Fennessy, was quoted as saying. "With a decline of almost 40% in the last three decades alone, the world's tallest across East, Central and West Africa. As one of the world's most iconic animals, it is timely that we take risks for the giraffe before it is too late." Of nine subspecies of giraffe, five are declining in numbers, while three have increasing populations and one is stable. 

According to the passage, 13 newly recognized bird species are listed as ___