The correct answer is regulate.
Modulate
A. render less violent
B. regulate
C. plot coordinates on chart
D. create in modular form
The correct answer is (B) To regulate, especially by varying the pitch; to adjust to a certain measure or proportion; to alter or adapt (the voice) to circumstances; to soften; to tone down..
Modulate comes from Latin modulari (to measure).
Examples of use:
- Her well-modulated voice was easily understood by her listeners.
- As he rehearsed, her modulated his delivery.