A) NO CHANGE B) that are helping C) who are helping D) who help

Consider the appropriate usage of relative pronouns. Remember that 'that' and 'which' are generally used for objects, while 'who', 'whom', and 'whose' refer to people. Understand the difference in meaning and usage between 'helping' (continuous action) and 'help' (simple action).

Analyze each of the provided options to determine which one would be most suitable to complete the sentence: A) NO CHANGE - Without the original sentence, it is impossible to determine if keeping the sentence as it is would be correct. B) that are helping - Using 'that' as a relative pronoun for a group of people is not ideal since it should be reserved for objects. C) who are helping - This option uses the correct relative pronoun, 'who,' to refer to a group of people engaged in the action of helping (continuous action). D) who help - In this option, the correct relative pronoun, 'who,' is used to refer to a group of people. However, the verb 'help' is in simple present tense, indicating a general action.

Based on the analysis of the options, the most appropriate solution would be either option C) who are helping or option D) who help, depending on the context of the sentence. Without the complete sentence, choosing one of the options becomes challenging. However, both C and D are grammatically correct, and the choice between them would depend on the specific context.