Final answer:
The correct word to complete the sentence is 'sung', as it is the past participle form of the verb 'sing' and fits properly with the auxiliary verb 'have' in the given sentence.
Step-by-step explanation:
The word that correctly completes the sentence is sung, option C. The base form of the verb 'sing' is used when it is the main verb in a sentence. However, in this sentence, we are looking for the past participle form of the verb, which is 'sung'.
An example sentence using 'sung' would be: 'Have you sung in the choir before?'The word that correctly completes the following sentence is 'Have you sung in the choir before?' So the correct answer is C) Sung. The word 'sung' is the past participle form of the verb sing, which is appropriate to use with the auxiliary verb 'have' in perfect tense constructions.