In the given sentence, a blank is given indicating that a word is missing.…

In the given sentence, a blank is given indicating that a word is missing. Among the four given options, a combination of words fit the blank thereby making it grammatically and contextually correct. Choose that option as your response.

Such parents __________ between saying no and giving in but neither response seems satisfactory to them.

A. Vacillate

B. Terminate

C. Quiver

D. Waver