1l.ACD因为8cos2a-2cos2(B+C)-7=0.所以4(1+co1)-2cos2(x-A)-7=0,所以4cosA-4cosA+1=0,即(2cos4-1)2=0,解得c0sA=1,因A∈(0x),所以A√33,所以sinA=又因为a=2,由余弦定理得:a2=分+c2-2bcos4=b2+c2-bc≥bc,所以bc≤4当且仅当b=c时,取等号,则△ABC面粤S△=1 basin≤2×4×3=3,所以△ABC面积的最大值为3.又b2+3bc≤3×即(b+c4十得b+4,故△ABC周长的最大值为6.故选ACDMN

书面表达One possible version:Dear Mr. Smith.First of all, I would like to congratulate you on your school s sixtieth anniversary. The long history of theschool brings up its outstanding campus culture and educational concept. I take great pride in studying at thisexcellent school, At your invitation, I will perform a Chinese folk dance at the celebration ceremony to expressmy congratulations. Please prepare the audio equipment to play the accompanying music. I will prepare thedance music and costumes myself. I am delighted to be able to make a modest contribution to the promotion ofChinese culture and cultural exchanges between China and the UKBest wishes.Yours truly,Li Hu

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