Dr. Yang studies cross-cultural differences in body maturation and growth, including differences in body size, proportion, appearance, health, and perceptual abilities. Dr. Yang is interested in development.

The answer is Human Physiological development.

Explanation:

Human physiological development is a study of how the human body matures, and grow in size. Since Dr. Yang is studying multi cultural differences, then he would bee interested in  body sizes, proportions, appearances, health and perceptual abilities of various cultures in the world.

Physical development is the answer. Therefore,

Dr. Yang studies cross-cultural differences in body maturation and growth, including differences in body size, proportion, appearance, health, and perceptual abilities. Dr. Yang is interested in physical development.

Refer below for the explanation.

Explanation:

Physical development refers to the changing of body, mind, appearance, health.

there is not such an "uncle" in the poem "a servant to servants". the narrator refers to many characters -particularly her brother and her husband- both suffering from mental illness. the woman is also suffering because she does something to but she is not happy with the situation.

the poem has a dramatic monologue about the woman life's circumstances and her traumatic events form the past.

"a servant to servants" is a poem written by robert frost, and is part of a collection of poems "north of boston", of 1915.