一篇高中英语完型的问题
AsIamnowsixteenyearsold,Ihaveagreatmanyfriends.ButoneofthemIlikebestofall.I'veknownhimsinceIwasamiddleschoolstudent.Heisamanofasweetandsofttemper,buthelooksverysolemn(严肃).Hesometimesappearsveryoldandsometimesveryyoungandbright.Butheisalwaysclever.Heispleasedbyallwhoknowhim.
Heisalearnedman.Heknowseverything.Moreover,hismemoryisverygood.Herememberswhateverhashappenedintheworld.Heisalsoagreatteacher.Hehastaughtmillionsofyoungmen.Therefore,heisknowntoeverybody.
Heismybestteacherratherthanmybestfriend.WhenIbegantogotoschool,hetaughtmehowtoreadandwrite.WhenIwasatmiddleschool,hebegantoteachmeEnglish,history,geography,physics,mathsandchemistry.
Myfriendisapatient(有耐心的)man,indeed.StupidasIam,heisnevertiredofteachingme.HeisalwaysreadytoteachmetillIamperfectlyfamiliarwithmylessons.Butthereisonethingwhichyoumaybesurprisedtoknow.ThoughIhavelivedwithhimforalongtime.I'veneverheardhisvoice.WheneverIaskhimquestions,heneveranswersthemwithhismouth,butshowsmetheansweronhisface.
Heisnotonlymybestfriend,butthebestfriendofmanyothers,includingyouofcourse.I'msureyoualsoknowhimquitewellandyourloveforhimisgreat.
Whatisthismanthen?
请问这个人是谁啊?