Answer:
d. slow to warm up
Step-by-step explanation:
Thomas and Chess recognizes children's behavior by the temperamental types --
-- easy,
-- difficult,
-- slow-to-warm-up.
But contemporary developmental scientists have identified nine traits to define the mood or behavior of the children. Some of the nine traits are positive emotionality, effortful control and negative emotionality.
Thus the answer is --
d. slow to warm up