Topic: Preposition,

Best Answer Explained in Below-:

The correct preposition in the sentence "He spent most of his life ___ Dhaka" is "in," making the complete statement "He spent most of his life in Dhaka."

Using "in" is appropriate here because it indicates being inside or within a specific geographical location, which in this case is the city of Dhaka. When referring to cities, countries, or large areas, "in" is the standard preposition employed to denote where someone lives or spends a significant amount of time.

On the other hand, "at" generally refers to a specific point or location, typically smaller or more defined than a city, making it less accurate in this context. For example, we might say, "He was at the park," but not "at Dhaka." The preposition "over" is typically used to signify duration or coverage over time or an area, but it does not conventionally fit with places in the context of residence or life spent there.

Thus, the preposition "in" effectively communicates the idea of residing or spending significant time within a defined space, which makes it the correct choice in this instance.