Baby polly was usually a calm, happy baby when she is around her parents and siblings. when her parents took her to a family reunion, however, her behavior changed. her face crinkled up in a frown and she stared at stranger with suspicion. A. baby polly was demonstrating an example of distress. B. nonverbal encoding. C. stranger anxiety. D. emotion.

C. stranger anxiety

Explanation:

In psychology, the term stranger anxiety refers to the phenomenon where infants feel distress or anxiety when they are around people who are unfamiliar to them. In other words, they feel distressed or afraid around people who they don't know.

In this example Baby Polly is usually a calm, happy baby around her parents but when they took her to a family reunion, her behavior changed and she stared at strangers with suspicion. We can see that Polly is reacting with distressed and fear around people who she doesn't know and therefore this would be an example of stranger anxiety.  

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.

answer; a cost benefit analysis;