条件等式可化为(a-5)²+[-1+√(b-4)]²+|-2+√(c-1)|=0.===>a-5=0,且-1+√(b-4)=0,且-2+√(c-1)=0.===>a=5,b=5,c=5.故该⊿为等边⊿.选B.