Oh! Trivia Quiz

Answer:

I have thought of words which are homophones of eighteen of the twenty-six letters of the English alphabet.
A sounds like 'eh', which is used in British English as a slightly impolite request for something to be repeated. In a similar vein is 'what?'; children are taught that the correct wording is 'I beg your pardon'. In Canada, the word is used as an interjection at the end of a sentence. In the USA, 'eh' sometimes has a different pronunciation. A is also used as an indefinite article.
B sounds like 'be' and 'bee', as used in the story.
C sounds like 'sea' and 'see', which are also both in the story.
D sounds like the name, Dee, which is used for both people and places, but not things, so I haven't counted it.
E sounds like 'eeh', which is used in the Yorkshire expression 'eeh ba gum'. It means 'by God', and is described as a minced oath, since it could be said without taking the Lord's name in vain.
G sounds like 'gee', which is used as a command for a horse to speed up, and as an expression of surprise in North America.
I sounds like 'aye' and 'eye', as well as being used as a personal pronoun. Aye is used to signify agreement; when repeated it becomes a nautical term of obedience. An eye is an organ of sight, and is also used to refer to the centre of a something such as a storm.
J sounds like 'jay'. Jays are birds which are found in many parts of the world, although blue jays are from North America. The Toronto Blue Jays are a baseball team.
K sounds like 'Kay', which is used as both a first name and a last name, but it's not a thing, so I haven't counted it here.
L sounds like 'ell'. An ell is an old measurement of length, mainly used for cloth, and equivalent to about forty-five inches. The word is also used for an extension to a building set at right angles to the original structure.
M sounds like 'em', which is a printing measurement.
N sounds like 'en', which also a printing measurement, half the size of an em.
O sounds like 'oh' and 'eau'. Oh is an exclamation as used for the title of this quiz, and at the beginning of the story. Eau is the French word for water; it is used in English in eau de cologne, which is a light perfume.
P sounds like 'pea', a green vegetable referenced in the story, and 'pee', which is a slang term meaning to urinate.
Q sounds like 'queue'. Nowadays, in Britain and other places it refers to a line of people waiting for something. In past times it described a man's hair style, which would probably be known as ponytail today.
R sounds like 'are' - part of the verb 'to be'. In some forms of English it also sounds like the exclamation 'ah'.
T sounds like 'tea' and 'tee', as used in the story. It is also used in English for T-bone steaks, T-shirts, and T-squares.
U sounds like 'ewe' and 'yew', as in the story, and sounds like the personal pronoun 'you'. It is also used in plumbing for a U-bend, and on the road for a U-turn.
V is used to describe a style of clothing, as in V-neck, but doesn't get used as a separate word, so I haven't counted it.
X sounds like 'ex', which is used to refer to a former partner.
Y sounds like 'why', as used in the story, although it can also be used to start a question.