Which of the Following Statements Represents an Operational Definition

Which of the following statements represents an operational definition?

A) Spirituality is a way of being or experiencing that comes about through an awareness of a transcendent dimension and one's identifiable values with regard to self, other, nature, and whatever one considers to be ultimate. (Elkins, 1988)
B) Death anxiety is an uncomfortable feeling upon contemplation of one's own death (Templer, 1986) , measured by Templer's Death Anxiety Scale.
C) Maternal identity entails maternal cognitions and affect with regard to the maternal-infant relational system. (Walker and Montgomery, 1994)
D) Pain is a pattern of responses to protect the organism from harm. (Sternbach, 1979)