The correct option is A The
Option A: 'The' is a definite article that modifies nouns that are
specific. This means that the identity of that noun is made known. In
the passage, the identity of the noun 'man' is made known by the words that follow 'who had ___ idea to start ___ office was George Everest.'
Hence, the noun is made specific and 'the' is the most
suitable article.
So, option A is correct.
Options B and C: 'A' and 'an' are both indefinite articles. They refer
to nouns that are not specific. This means that we do not know the
identity of the noun. For example, 'a book', 'an elephant', etc.
(The
only difference between 'a' and 'an' is that 'a' is used for nouns that
begin with a consonant, like 'b' in book', and 'an' is used for nouns
beginning with a vowel, like 'e' in 'elephant'.)
The noun here 'man' refers to a particular person 'George Everest'. Hence B and C are incorrect.
Option
D: An article is not required when the noun is spoken of in general
sense, and when the noun is uncountable. The word here is neither, hence
D is incorrect.