Nowadays, scientists are working hard to find a best way of treating addictions __________ drugs.

 Nowadays, scientists are working hard to find a best way of treating addictions __________ drugs.

  A. of             B. in            C. on            D. to

Nowadays, scientists are working hard to find a best way of treating addictions __________ drugs.

  A. of             B. in            C. on            D. to

Nowadays, scientists are working hard to find a best way of treating addictions __________ drugs.

Nowadays，scientists are working hard to find a best way of treating addictions ________ drugs.