OG20一题求帮助！

Althoughsome had accused Smith, the firm’s network manager, of negligence when thecrucial data went missing, the CEO defused a situation that was quite tensewith her public statement that the debacle was not Smith's fault.
A. a situation that was quite tense with her public statement that the debaclewas not Smith's fault

B. a situation that was quite tense, by publicly stating that the debacle wasnot Smith's fault
C. a situation,which was quite tense, by stating publicly that Smith was not responsible forthe debacle

D. aquite tense situation with a public statement about the debacle not beingSmith's fault
E. a quite tense situation by publicly stating the debacle not to have beenSmith's fault

B选项中的, by publicly stating that

1.为什么会在前面有逗号？

2.Gmat club上有人说是ADV Modifier 我目前还没有见过这样的类型

感谢感谢