Directions: In the following question, a statement with an underlined phrase is given. Choose the most appropriate option from the choices provided to replace the underlined phrase, making the sentence grammatically and contextually correct. If the underlined phrase is already correct, select "No correction required".

The library closes every weekend at 8 p.m. and reopens on Monday morning.

The correct answer is No correction required.

Step-by-step Explanation:
1. Analyzing the Sentence Structure:
The given sentence is: "The library closes every weekend at 8 p.m. and reopens on Monday morning."
We need to check the underlined phrase "every weekend at 8 p.m." for proper grammar, determiner usage, and prepositional accuracy.

2. Grammatical Rules Breakdown:
• Determiner 'every': The word "every" is used to refer to all members of a group or recurring events individually. It must be followed by a singular countable noun. Here, "every weekend" correctly uses the singular noun "weekend".
• Preposition of Time ('at'): In English grammar, the preposition "at" is used to denote specific points in time on a clock (e.g., at 8 p.m., at 3:00, at noon). Using "in", "on", or "from" in this context without an ending time bound is grammatically incorrect.

3. Evaluation of Options:
• each weekend on 8 p.m.: Incorrect because the preposition "on" is used for days/dates (e.g., on Sunday), not for specific times of day.
• No correction required: Correct because "every weekend at 8 p.m." uses the correct singular form "weekend" along with the accurate preposition "at" for time.
• every weekends at 8 p.m.: Incorrect because "every" cannot be paired with the plural noun "weekends".
• every weekend in 8 p.m.: Incorrect because "in" is used for months, years, or periods of time (e.g., in July, in the morning), not specific clock times.
• every weekend from 8 p.m.: Incorrect because "from" requires a starting point and typically pairs with "to" or "until" (e.g., from 8 p.m. to 10 p.m.) to indicate a duration.

Hence, the underlined phrase is completely correct as written.