In the following passage, some words have been deleted. Read the passage carefully and
select the most appropriate option to fill in each blank.

Darwin planned to (1) ________ a book describing his (2) _________. He spent nearly twenty years (3) ________ the matter for his book, which was to deal with every known fact concerning the problem of the species. Unluckily for Darwin, a naturalist named Wallace had been (4 ) _________ over the same problems and had reached the same solution. He sent Darwin an essay which almost word for word repeated Darwin's own ideas. Yet Wallace, who was an (5) ________ , had been working far away in the Malay Archipelago, whilst Darwin had not left England for several years.