The most common known sleep disorder is

After moving to a new city, seven-year-old Marta tended to cling to her mother whenever they went to the playground, never venturing more than a few feet away

When school started, Marta would beg her mother to walk the two blocks with her every morning and afternoon rather than walking with the older daughter of a neighbor. Marta told her mother that she was afraid the older child would get her lost and then she would never see her parents again. Marta appears to be showing signs of a. inappropriate social referencing. b. an insecure-avoidant attachment. c. separation anxiety disorder. d. abnormal imprinting.

Of those listed, which is the most sensitive area based on the density of skin receptors?

a. face. b. thigh. c. back. d. upper arm.