In the Last Man Case, Routley Has Us Imagine That

In the last man case, Routley has us imagine that, due to some disaster, there is only one man remaining on earth but plenty of plants and animals and life will go on after the last man's death. Routley thinks that we would intuitively judge it morally wrong for the last man to go on a killing spree of plants and animals. What does he think this judgment shows?

A) The virtue of temperance is morally serious.
B) Cruelty is a vice.
C) Nature has only instrumental value.
D) Nature has intrinsic value.