Fill in the blanks with the most appropriate option.
The boy fell ___ the bicycle.
A) of
B) off
C) from
D) under

Hint: A preposition is a word or set of words that comes before a noun, pronoun, or noun phrase to indicate direction, time, place, location, spatial relationships, or to introduce an object. Words like "in," "at," "on," "of," and "to" are examples of prepositions. In English, prepositions are extremely idiomatic.

Complete answer:
- Prepositions show how other words in a sentence are related.
- Many prepositions indicate the location of something or the time it occurred.
- Since most prepositions have several meanings, their interpretation varies greatly depending on the context.
- It is not a grammatical mistake to end a sentence with a preposition.
- For example: He sat on the chair. In this sentence, on is the proposition.

Now let us look at the given options:
A) of: This option is incorrect because it implies that you belong to something, that you are a part of something, or that you are related to something that isn't required in the sentence.
B) off: This is the correct option. It refers to moving away from and sometimes down from something; in this case, it's the bicycle.
C) from: This option is incorrect because It is used to indicate where someone or something begins, while we must suggest that we are heading away from the bicycle.
D) under: This option is incorrect because it implies that something is underneath the surface of something; that something is hidden by something that isn't needed in the sentence.

Thus, the correct option is ‘B’ i.e, ‘off’.

Note: Direction, time, place, and space relationships, as well as other abstract types of relationships, are all indicated by prepositions.
- Direction: Look to the left and you will see my house.
- Time: I have been working since morning.
- Place: We place a game at his house.
- Space: The cat is under the table.