Thumbs on front shoulders are an example of <u>an NMM (non-manual marker),</u> which must be done properly for a sign to be correct. The correct option is C.
<h3>What is an NMM (non-manual marker)?</h3>
Non-manual markers are signs that are used when speaking to saying something to other people or an audience. They enhance the remaining content, you are saying.
These signs are head tilting, shoulder raising, using of fingers, mouthing, and expressions. Lower body movements and the use of legs, or thighs, are restricted in this language.
Thus, the correct option is C. an NMM (non-manual marker).
To learn more about NMM (non-manual marker), refer to the below link:
brainly.com/question/11502767
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