We stayed _________ the Heathrow Hotel.
(Fill in the blank with a suitable preposition)
a. on
b. into
c. at
d. to

Hint: The student should read the sentence carefully to understand what the ‘Heathrow Hotel’ signifies. Then the options should be carefully distinguished to find their purpose, and whether they are used for the signification of words like ‘Heathrow Hotel’.

Complete answer: In this question, it will be helpful for the student to recall the concept of prepositions. A preposition is a function word that combines with a noun or pronoun or noun phrase to form a prepositional phrase that can have an adverbial or adjectival relation to some other word.
Let us analyze the options given to us in this question -
Option (a.), 'on', refers to ‘positioned at the upper surface of, touching from above’.
Therefore, option (a.) is incorrect as the ‘Heathrow Hotel’ is not something that can be stayed ‘on’, as it is a location/place and not a thing.
Option (b.), ‘into', refers to ‘going inside (of)’.
Therefore, option (b.) is incorrect as the given sentence does not indicate going inside something or somewhere.
Option (c.), ‘at', refers to ‘in or very near a particular place’.
Therefore, option (c.) is correct as the ‘Heathrow Hotel’ is a place, a location, and the preposition ‘at’ indicates that ‘we’ stayed in this place.
Option (d.), ‘to', refers to ‘indicating destination: In the direction of, and arriving at’.
Therefore, option (d.) is incorrect as the ‘Heathrow Hotel’ is talked about as a location, but not a destination.
Therefore, option (c) is the correct answer.

Note: Prepositional verbs are the phrasal combinations of verbs and prepositions which act as links between the verb and noun or gerund, giving extra meaning to the sentence. They can have slightly different meaning compared to the original verb.