Grocery Stores in the Toronto Area Attempted to Get Shoppers

Grocery stores in the Toronto area attempted to get shoppers to reuse their plastic shopping bags either by providing a 5-cent credit for doing so or by imposing a 5-cent tax for not reusing their bags.Which statement about the results of this policy is TRUE?

A) The credit but not the tax significantly increased bag reuse.
B) The tax but not the credit significantly increased bag reuse.
C) Both manipulations equally increased bag reuse.
D) Both manipulations significantly increased bag reuse,but the tax was more effective.