We have to find a statement which supports the opinion that exercise leads to better efficiency.Choice (a) talks about the work environment but not about physical exercise. Hence, (a) does not support the opinion.Though choice (b) states that physical exercise is important, it does not state whether the physical exercise improves the performance or helps to maintain the performance levels.Choice (c) states that those who does physical exercise exhibit better performance rather than those who does not. Hence, (c) supports the opinion.Choice (d) refers to monotony in work but not about physical exercise. Hence, (d) is out of context.