Bats: past perfect (B2)
White-nose syndrome has killed millions of hibernating bats in North America since the fungus arrived from Europe, probably on the boots of a caver. The disease wakes the animals repeatedly during winter, forcing them to burn fat reserves at a season when there are no insects to replace them. One monitoring site in the north-east illustrates the speed of the collapse. Counts in November recorded a healthy population of little brown bats; by the time the survey team returned to the same cave in March, the fungus ___ more than ninety per cent of them. The economic argument for protecting bats is straightforward, since a single colony consumes tonnes of agricultural pests each summer, but the ethical argument matters too: humans carried the fungus across the Atlantic.
Fonte: English for ALL (texto original).
Assinale a alternativa que completa corretamente a lacuna do texto.
- A) has already killed
- B) have already killed
- C) had already killed
- D) would already kill
- E) had already been killed