EXERCISE 21-1 Using Active and Passive Voice Verbs
Revise the following passage, changing the passive voice to the active voice in each sentence, unless you can justify keeping the passive. Example:
The unique creatures of the Galápagos Islands have been studied by many scientists. The islands were explored by Charles Darwin in 1835. His observations led to theory of evolution, which he explained in On the Origin of Species. Thirteen species of finches on the islands were discovered by Darwin, all descended from a common stock; even today this variety of species can be seen by visitors to the islands. Each island species has evolved by adapting to local conditions. A twig is used by the woodpecker finch to probe trees for grubs. Algae on the ocean floor are fed on by the marine iguana. Salt water can be drunk by the Galápagos cormorant, thanks to a salt-extracting gland. Because of the tameness of these animals, they can be studied by visitors at close range.