Around 20% of all yearly deaths in the united states can be attributed to chronic use.
a. tobacco
b. heroin
c. cocaine
d. marijuana

Option a, tobacco.

Explanation: There is not death a cause of marijuana, so we can discard this option.

While substances like heroin or cocaine are way more harmful than tobacco, tobacco is more commonly used than other substances.

The deaths caused by tobacco are around 480,000 per year, where an estimated of 41,000 are caused by second-hand smoking.

Then the right answer is A.