Explain

The author notes there has been decline in yields, and then decides that this decline is a result of researchers' who are concerned only with their own research rather than the needs of the country. This is a pretty weak argument, there are any number of possible causes, and the author decides to focus in on one in particular. However, C is correct for a different reason. C gives us reason to suspect that by focusing on their own research, the researchers are actually contributing to work that is likely to inadvertently be beneficial.