Several Meta-Analyses Have Produced Similar Findings About the Effectiveness of Contingency

Several meta-analyses have produced similar findings about the effectiveness of contingency management in reducing use of various drugs,including tobacco.Their findings show that contingency management is:

A) not very effective in reducing drug use (e.g.,based on a low overall effect size) .
B) highly effective in changing drug use (e.g.,based on a very large overall effect size) .
C) moderately effective for reducing most drug use,but less so for tobacco.
D) most effective in reducing tobacco use,and minimally effective with other (hard) drugs.