Complete the sentence: It was an American, in 1919. At _________ time, the bags were mainly used by tea companies to allow customers to try the tea before buying it.

Complete the sentence: It was an American, in 1919. At _________ time, the bags were mainly used by tea companies to allow customers to try the tea before buying it.

• A. This
• B. Which
• C. When
• D. That

Answer: (D)

The main idea is how we refer back to a specific moment in the past with a natural time expression. At that time is a common collocation meaning “during that particular period.” Since the sentence has just set the scene in 1919, using that time correctly ties the following clause to that same past moment, so the idea flows smoothly: the bags were mainly used by tea companies to let customers try the tea before buying it. Other options don’t fit this natural reference. This time would point to the present or a more immediate moment, which clashes with the historical context. When would require a different structure and wouldn’t sit properly after At. Which time isn’t a standard way to complete the sentence in this position, and that alone functions as a demonstrative determiner for time here.

The main idea is how we refer back to a specific moment in the past with a natural time expression. At that time is a common collocation meaning “during that particular period.” Since the sentence has just set the scene in 1919, using that time correctly ties the following clause to that same past moment, so the idea flows smoothly: the bags were mainly used by tea companies to let customers try the tea before buying it.

Other options don’t fit this natural reference. This time would point to the present or a more immediate moment, which clashes with the historical context. When would require a different structure and wouldn’t sit properly after At. Which time isn’t a standard way to complete the sentence in this position, and that alone functions as a demonstrative determiner for time here.