The correct answer is: E. has become/includes.
Alcoholism is a leading cause of death of the young adult population in the USA. This statistic includes deaths from drunken driving and fires started by carelessly dropped cigarettes.
Option A is incorrect because the past tense “became” is not used to describe a current situation.
Option B is incorrect because the present tense “becomes” is not used to describe a past situation.
Option C is incorrect because the past progressive tense “was becoming” is not used to describe a current situation.
Option D is incorrect because the present progressive tense “is becoming” is not used to describe a past situation.
Option E is correct because the present perfect tense “has become” is used to describe a current situation.