Select the correct alternative to fill in the blank with the correct preposition in the following sentence.

The head architect exerted a remarkable authority ________ the architectural designs chosen for the urban project.

The correct answer is over.

Step-by-Step Explanation:

1. Analyze the Context of the Sentence:
The given sentence is: "The head architect exerted a remarkable authority ________ the architectural designs chosen for the urban project."
Here, we need to choose the appropriate preposition that correctly pairs with the noun "authority" when indicating power, influence, or control regarding a domain or project.

2. Understand Prepositional Usage with "Authority":
In English grammar, when the noun authority is used to describe control, power, or command held by a person over something or someone, it is naturally followed by the preposition "over" (i.e., to have or exert authority over someone/something).

3. Evaluate the Given Options:
• over: Correct. It properly completes the phrase "authority over," showing control and power regarding the chosen architectural designs.
• against: Incorrect. "Against" implies opposition, resistance, or hostility, which does not convey exercising control.
• beneath: Incorrect. "Beneath" means lower in position or rank, which contradicts the concept of having control or authority.
• beside: Incorrect. "Beside" means by the side of or next to, which does not fit the grammatical context of exerting control.

Conclusion:
Inserting "over" makes the sentence grammatically sound and meaningful: "The head architect exerted a remarkable authority over the architectural designs chosen for the urban project."