… the hours of nine and ten, the surgeons completed the operation.

Analyze the question

The sentence is: "__ the hours of nine and ten, the surgeons completed the operation." We need a word that correctly links "the hours of nine and ten."

Explain the concept

When two points or limits are named with "and," the correct preposition is between. "Between" is used to show a position or range involving two (or more) separate things, times or points. It is followed by "and" (never "to" or "or").

Examples:

• Between 2 p.m. and 4 p.m.
• Between Lagos and Abuja.

Step-by-step solution

1. Notice the phrase "the hours of nine and ten". The "and" signals a range with two limits.
2. Test each option: • A. before: "Before the hours of nine and ten" doesn't make sense, because it doesn't fit a time range with two limits. • B. upon: "Upon the hours of nine and ten" is unnatural and incorrect in this context. • C. between: "Between the hours of nine and ten, the surgeons completed the operation" is correct and natural. It means the operation was completed at some point within that one-hour period. • D. in: "In the hours of nine and ten" is not idiomatic. "In" would not pair with "and" to show a range.
3. The only option that works with "and" to show a time range is between.

Correct answer: C. between

Exam tip: Whenever you see "___ X and Y", think between. Remember the pair: between... and... (and from... to...). If you see "and" after the blank, "between" is almost always the answer.