Sentence Correction

Indonesia's Mount Merapi volcano has killed 191 people since it began erupting late last month, leading to the declaration of an emergency in the country

A. has killed 191 people since it began erupting late last month, leading to the declaration of an emergency in the country
B. killed 191 people since it began erupting late last month, leading to the declaration of an emergency in the country.
C. has killed 191 people since it began erupting late last month, which has lead to the declaration of an emergency in the country.
D. had killed 191 people since it began erupting late last month, leading to the declaration of an emergency in the country.
E. has been killing 191 people since it began erupting late last month, leading to the declaring of an emergency in the country.

OA is A
Pls i need an expert help to explain the verb tense agreement here. Thanks for your help