I want to know: Why did Allah create life and death?

Allah created death and life to test people as to which of them is best in deed. Allah has humbled the son of Adam with death, and He made this world a transient abode and the Afterlife an eternal abode of recompense. So, Allah causes to die whom He wills and brings to life whom He wills for a known term, to test which of His servants is more obedient and quicker to seek His pleasure. This trial is for the purpose of realizing servitude to Allah.