Difficulty: Easy
Correct Answer: from last 12 years.
Explanation:
Introduction / Context:
This question tests correct preposition and time expression with perfect/progressive tenses. English requires particular prepositions with time spans depending on whether we refer to a starting point or a duration.
Given Data / Assumptions:
Concept / Approach:
Use “for” + duration (for two hours, for three weeks). Use “since” + starting point (since 2012, since last June). “From” is not used with present perfect to mark duration; it would require a paired “to” (from X to Y) or a different construction.
Step-by-Step Solution:
Verification / Alternative check:
Correct sentence: “The historian has been working on the project for the last 12 years.” A valid alternative with a starting point would be “since 2012/2013,” etc.
Why Other Options Are Wrong:
Common Pitfalls:
Confusing “from” with “for.” “From” typically pairs with “to/till/until,” not with an open-ended duration in perfect tenses.
Final Answer:
from last 12 years.
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