public class Zoo 
    {
        public Guid ID { get; set; }
        public virtual ICollection<Animal> Animals { get; set; }
    }

    public class Nation
    {
        public Guid ID { get; set; }
        public string Name { get; set; }
    }
    public  class Animal
    {
        public Guid ID { get; set; }
        public int Age { get; set; }
        public virtual Nation BornNation { get; set; }
    }

    public class MyDBContext : DbContext
    {
        public MyDBContext()
        {
            this.Database.EnsureCreated();
        }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            base.OnConfiguring(optionsBuilder);
            optionsBuilder.UseSqlServer(@"Server=CRM3-NB01\SQLEXPRESS;Database=TestEF;Trusted_Connection=True;");
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            base.OnModelCreating(modelBuilder);
            modelBuilder.Entity<Animal>().HasKey(itm => itm.ID);
            modelBuilder.Entity<Animal>().HasOne(itm => itm.BornNation).WithMany().IsRequired(false);
            modelBuilder.Entity<Zoo>().HasKey(itm => itm.ID);
            modelBuilder.Entity<Zoo>().HasMany(itm => itm.Animals).WithOne().IsRequired(false);
            modelBuilder.Entity<Nation>().HasKey(itm => itm.ID);
        }
    }

using (var DB = new MyDBContext())
            {
                var q = (from itm in DB.Set<Zoo>().Include(itm => itm.Animals.Take(10)).ThenInclude(itm => itm.BornNation) select itm ).FirstOrDefault();
            }