Select the most appropriate option to substitute the underlined segment in the given sentence. If there is no need to substitute it. select No improvement.

A phenomenon called the polar vortex has hit central and eastern parts of the United States. It has brought with it snow, brutally cold temperatures and potentially life—threatening wind chill.

A

potentially life-threaten windy chills.

B

No improvement

C

potentially life—threatened wind chill.

D

potential life—threatening wind chill.