The correct answer is A. A dozen people filled 50 trash bags in only two hours
Step-by-step explanation:
In writing, the word "elaboration" refers to adding details or expanding the information about some topic, issue or situation in a detailed way usually by using descriptions, examples, details, analogy, evidence, among others that allows the reader to get more information about the topic being described. This means if you are required to elaborate on the sentence "We cleaned up the creek" it is expected you add precise details and more information related to the process of cleaning the creek such as the steps of the process, the outcome, among others.
Considering this, the best statement that elaborates on this sentence is "A dozen people filled 50 trash bags in only two hours" as this is directly related to the process of cleaning the creek and also is the most detailed one as adding details such as "50 trash bags" and "two hours" provide more information to the reader to understand the topic.