Explanations:In English grammar, prepositions are used to indicate the relationship between a noun or pronoun and other parts of the sentence. One common use of prepositions is to specify time. Different prepositions are used for different types of time expressions. For example, "in" is used for larger time periods such as months, years, or seasons, while "on" is used for specific days, and "at" is used for specific times.
When referring to specific days, such as days of the week, holidays, or dates, the preposition "on" is the correct choice. For instance, we say "on Monday," "on Christmas," or "on the 25th of December." This usage helps to pinpoint a particular day within a larger time frame. The preposition "on" is used to indicate that the action (in this case, eating out) occurs on a specific day, which is Sunday.
It is important to note the distinction between the prepositions "on," "in," and "at" when referring to time. "In" is used for larger time periods, such as "in January," "in 2023," or "in the summer." "At" is used for specific times, such as "at 3 PM," "at midnight," or "at the stroke of midnight." Using the correct preposition is crucial for clarity and grammatical correctness in English.
Common mistakes include using "in" instead of "on" for specific days, using "at" instead of "on" for specific days, or not using any preposition at all when referring to specific days. These errors can lead to confusion and grammatical errors in writing and speaking.
Therefore, the correct answer to the question "They eat out ..... Sundays" is "on," as it correctly indicates that the action of eating out occurs on a specific day, which is Sunday.