Concept:The phrase combines a direct comparison using "like" and an implied comparison of the facial expression to a rigid mask.
Explanation:A simile is a figure of speech that compares two things using "like" or "as".
Here, the deadpan look is directly compared to a death-mask with the word "like".
This makes the phrase a simile.
A metaphor is an implied comparison without using "like" or "as".
The word "plastered" suggests that the look is artificially fixed onto their faces like a mask.
This creates a metaphorical image of an emotionless, stiff expression.
Therefore, the expression uses both metaphor and simile.
Answer:D. metaphor and simile