选D由正弦定理有a/sinA=b/sinB=c/sinC设k=a/sinA=b/sinB=c/sinC则a=ksinA,b=ksinB,c=ksinC所以a:b:c=1:2:3不过这题有问题，a:b:c=1:2:3是不可能的，a+b=c矛盾
