420. There is no doubt that students who are athletically inclined will reap the most benefits from a policy that requires physical exercise to be part of every school day.
there is no doubt that...使用了一个主语从句，表示“毫无疑问的是……”，who引导定语从句，修饰students；that同样引导定语从句，修饰policy。reap意为“获得，得到报偿”，reap profits/benefits from/through意思是“从……获得利润/利益”。也可以使用以下这些句型表达同样的意思：
There is no denying the fact that...
No one can deny the fact that...
No one can doubt the essential fact that...
It is indisputable that...
It is an undeniable fact that using tobacco will be harmful to your health.
There is certainly no denying that stricter penalties may to some extent bring down the number of accidents on motorways as a deterrent to driving offences.
No one can deny the fact that a person's education is the most important aspect of his life.