Which of the Following Describes the Concept of Extended Deterrence

Which of the following describes the concept of extended deterrence?

A) A few nuclear weapons are kept in order to retaliate and inflict unacceptable damage on an adversary.
B) Many nuclear weapons are kept in order to deter both conventional and limited nuclear attacks.
C) Nuclear weapons are kept to deter an attack on the territory of an allied country.
D) Nuclear land-, sea-, and air-based retaliatory weapons are kept to defend a country.