Sevan, age 11 months, is wary of strangers. However, when his mother sits on the floor, Sevan ventures a few feet away from her for a few minutes at a time, and then returns to her for emotional support. Sevan is:.A) engaging in effortful control. B) exhibiting unusual behavior for a toddler with stranger anxiety. C) using his mother as a secure base. D) displaying avoidance rather than approach.