利用三目运算符：

#include <bits/stdc++.h>

using namespace std;

int main()
{
    string a, b, c;

    cin >> a >> b >> c;

    if ( a == "vertebrado")
    {
        if( b == "ave")
            ( c == "carnivoro")? cout<<"aguia"<<endl : cout <<"pomba" << endl;
        else
            ( c == "onivoro")? cout<< "homem" <<endl : cout <<  "vaca" << endl;
    }
    if ( a == "invertebrado")
    {
        if( b == "inseto")
            ( c == "herbivoro")? cout<<"lagarta"<<endl : cout <<"pulga" << endl;
        else
            ( c == "onivoro")? cout<< "minhoca" <<endl : cout <<  "sanguessuga" << endl;
    }
    return 0;
}