Answer:

Introduction:
In this question, we are given a sentence that says "We greeted our friends _____." and we need to choose the correct option to complete the sentence. The options provided are a) Happily, b) Happyc) Happyly.

Explanation:
To determine the correct option, let's analyze each option one by one:

a) Happily:
The word "happily" is an adverb that describes the way in which an action is performed. Since greeting someone is generally considered a pleasant and joyful action, it would be appropriate to use the adverb "happily" to describe how we greeted our friends. Therefore, option 'A' is the correct answer.

b) Happy:
The word "happy" is an adjective that describes a feeling or state of being. While it can be used to describe the emotions we felt while greeting our friends, it does not fit grammatically in the sentence as it does not modify the verb "greeted" directly. Therefore, option 'B' is incorrect.

c) Happyly:
The word "happyly" is not a recognized word in the English language. It seems to be an incorrect form of the adjective "happy". Therefore, option 'C' is also incorrect.

Conclusion:
Based on the explanation above, the correct option to complete the sentence is 'A' - Happily. This option accurately describes the manner in which we greeted our friends.