A.a≠b≠c,α=β=γ=90° B.a=b≠c,α=β=γ=90° C.a=b=c,α=β=γ=90° D.a≠b≠c,α≠β≠γ≠90°
A.5 B.6 C.7 D.8
A.2n B.2n+1 C.n+1 D.n