Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions.The poaching crisis wiping out Africa's elephants is costing the continent's economies millions in lost tourism revenue, according to a new study. Researchers looked at visitor and elephant data across 25 countries, and modeled financial losses from fewer visitors in protected areas due to the illegal wildlife trade, which has caused elephant numbers to plummet by more than 100,000 ...

Read the following passage and mark the letter A, B, C or D to indicate the correct answer to each of the questions.

The poaching crisis wiping out Africa's elephants is costing the continent's economies millions in lost tourism revenue, according to a new study. Researchers looked at visitor and elephant data across 25 countries, and modeled financial losses from fewer visitors in protected areas due to the illegal wildlife trade, which has caused elephant numbers to plummet by more than 100,000 in the last decade. (A)

The study team combined visitor numbers across 164 protected areas in 25 countries in forest and savannah elephants, and elephant population data from 2009 to 2013, to reach a “per elephant" value in terms of tourism income.

They concluded that Africa was most likely losing $26m in tourism revenue a year. (B) Around $9m of that is lost from tourists' direct spending, such as staying at hotels and buying crafts, with the rest through indirect value in the economy such as farmers and other suppliers supporting the tourist industry.

The study, published in the journal Nature Communications, found that in most cases the revenue losses were higher than paying for stronger anti-poaching measures to keep elephant populations stable. (C) Dr. Robin Naidoo, the paper's lead author and , senior conservation wildlife scientist at WWF and his team found. In the case of central Africa's forest elephants, which are harder for tourists to see and therefore attract fewer visitors, the costs of protecting them exceed the benefits from tourism. Demand from south-east Asia has seen the price of ivory triple since 2009 and it is estimated that one elephant is killed every 15 minutes. (D) Corruption, a lack of resources, and, most importantly, increasingly sophisticated poachers have hamstrung African countries' efforts to stem the trade.

Naidoo said that the research was not suggesting economic issues should be the only consideration when protecting elephants, but framing the poaching crisis as a financial one could motivate African governments and communities.

“It gives an additional reason for some groups of people, who may not necessarily be motivated by intrinsic reasons for conversation, to engage with biodiversity conservation. It makes it clear to them that it's not just in the best interests of the world to conserve this stuff, but tangible reasons for a whole different group," he said.

Question. The word plummet in paragraph 1 is closest in meaning to ____.