To kill the creature, may be viewed as a cruelty but because of many factors that we have to kill it to survive in life, to the development of scientific progress.
Killing creatures and then may be viewed as cruel, but due to several factors that we need to kill it for survival of life to the development of scientific progress.
Killing creatures it may seem cruel, but because of many factors as we must kill him in order to survive your life to the development of a scientific breakthrough.