Correct option is C
The correct answer is
(c) but when she did she realized that she.
Explanation:
The sentence is describing a past event. Therefore, the correct verb form is "did" and "realized" instead of "does" and "realizes." This aligns the tense properly with the rest of the sentence.
Corrected sentence:
She opened her mouth to say something,
but when she did she realized that she couldn't find any words to express her surprise.