To answer this question, you need to understand verb tenses and subject-verb agreement. Let's go through each option to understand why it is correct or incorrect:
Option A) "packing" - This option is incorrect because it is in the present participle form, which does not match the subject "we" in the sentence.
Option B) "packs" - This option is incorrect because it is in the present tense form, which does not match the subject "we" in the sentence.
Option C) "packed" - This option is correct because it is in the past tense form and matches the subject "we" in the sentence. The verb "packed" indicates that the action of packing has already been completed.
Option D) "pack" - This option is incorrect because it is in the present tense form, which does not match the subject "we" in the sentence.
The correct answer is option C) "packed". This option is correct because it is in the past tense form and matches the subject "we" in the sentence. It indicates that the action of packing has already been completed for the trip to Europe.