If you mate a bull from who you expect 600 lbs. average weaning weight calves to cows that average 400 lb. weaning calves, yet the calves average a 540 lb. weaning weight, the additional 40 lbs. over the average of the parents is due to ________.
1) High heritability of weaning weight
2) Unexpected environmental effects
3) Heterosis
4) None of the above