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Question

Difficulty: MediumVerbs, Tenses, and Aspect

Fill in the blank with the grammatically correct verb form to complete the sentence.

Answer:By the time the expedition leader reached the base camp, the research team 【had been surveying】 the surrounding terrain for more than two weeks.

Answer

The correct verb form to fill the blank is 'had been surveying' (or 'had surveyed').
The past perfect continuous tense ('had been surveying') or past perfect tense ('had surveyed') is required because the action of surveying started and continued over a period of time before another completed past action ('reached').

Step-by-Step Solution

1
Analyze the time frame and temporal markers in the sentence.
The clause 'By the time...' coupled with the simple past verb 'reached' sets a past point of reference, while 'for more than two weeks' indicates continuous duration prior to that past point.
An action that began and continued before a specific point in the past requires the past perfect or past perfect continuous aspect.
2
Select the appropriate tense form.
The past perfect continuous form 'had been surveying' (or past perfect 'had surveyed') correctly establishes the prior duration of the action relative to the leader's arrival.
Simple past or present tenses create a sequence of tenses error when anchored to a past event.

Key Concept

Past Perfect and Past Perfect Continuous Aspect in Past Temporal Sequences
Estimated Time:1m 0s
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Topics

Verbs, Tenses, and Aspect

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