In the following question, a sentence / a part of sentence is underlined. Below are given alternatives to the underlined part which may improve the sentence. Choose the correct alternative. In case no improvement is required, choose "No Improvement" option.
She was completely nonplussed by the erratic behaviour of her father.

Options

A. completely plussed
B. completely no-nonplussed
C. entirely not nonplussed
D. No improvement