As the use of the plural pronoun 'their' in the claim preceding [9] is a reference to the astronomers working at the Maragha observatory in Persia, option C would best befit the context here as it specifically names one of the astronomers working at the Maragha observatory. The other options are either irrelevant or serve the opposite purpose of what is asked in the question. Additionally, the passage talks about how the scientists of the medieval Islamic world also contributed to the various fields of natural science so it would follow that option C would make the claim preceding [9] stronger. Option C is the answer.