Which of the following would be considered a sign of secure attachment in a 1-year-old?

a. Showing no sign of stranger anxiety, whether the parent is present or not

b. Paying no attention to a parent who returns after a brief separation

c. Showing anger at the parent after a brief separation

d. Becoming distressed when the parent leaves and seeking contact on return

e. Not reacting to a parent leaving or returning after a brief separation