2.What can we know about the retina? A、lt causes serious diseascs B、lt indieates the risk of death C、lspeeds pathological processes D.limproves people's physical health 33、How do researchers know the retinal age? A.By examining the nerve tissuc B、By studying the human brain C.By checking the eyesight D.By analyzing fundus images. 34、What pereentage of the participants had the largest retinal age gap? C.28% B.4.5% D.519 A.3.5%