The correct answer is option 'C' because it is the only option that is complete and makes sense on its own.

Let's break down the options and analyze each one:

a) This option is incomplete as it does not provide any information or context. It is just a single letter without any accompanying text. Therefore, it cannot be considered as a correct answer.

b) Similar to option 'a', this option is also incomplete as it does not provide any information or context. It is just a single letter without any accompanying text. Hence, it cannot be considered as a correct answer.

c) This option is the correct answer as it is the only one that provides a complete and meaningful response. The empty parentheses suggest that there is some missing information or a blank to be filled in. It indicates that there is some context or question that requires a response or an answer. This option is the most appropriate one among the given choices.

d) This option is incomplete as it does not provide any information or context. It is just an empty space without any accompanying text. Thus, it cannot be considered as a correct answer.

In summary, the correct answer is option 'C' because it is the only option that provides a complete and meaningful response, indicating the presence of missing information or a blank to be filled in.