The correct answer to fix the error in the sentence is option B: 'assembled.' This option aligns with the past timeframe indicated by 'last weekend.' Other options do not match the past tense required for the sentence.
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The verb tense in the sentence must match the time reference. Using "has assembled" corrects the error by indicating a completed action that aligns with the past reference of last weekend. Other options either do not convey the correct tense or mismatch the time reference. ;