An active lifestyleand a healthy,fish-rich diet are not only good for your heart,________(46),twoleading neuroscientists said on Wednesday.

As people livelonger,finding ways of halting the decline in mental agility is becomingincreasingly important,said professor Ian Robertson，_________(47).

"The biggestthreat to being able to function well and properly is ourbrains,"___________(48).

"There is verystrong evidence,___________(49),that the degree to which you maintain yourmental faculties depends on a handful of quite simple environmentalfactors,"he

said.

__________(50),avoidedhigh stress levels and enjoyed a rich and varied social life are betterequipped to stay alert as they age.Mental stimulation,learning new things and

simply thinkingyoung also help.________（49）

A.they may also helptackle the memory ioss associated with old age

B.he toldjournalists

C.director of the Institute of Neuroscienceat Trinity CollegeDublin

D.Those who remainedphysically fit

E.particularly inthe over-50s