Comparing emission taxes to emission standards, when polluters develop cheaper abatement technologies, how would the level of emissions change under

Comparing emission taxes to emission standards, when polluters develop cheaper abatement technologies, how would the level of emissions change under these two approaches if no adjustment is made by the regulator to the standard or to the tax rate following the innovation?

A     Level of emissions remain unchanged under both approaches

B     Level of emissions remain unchanged under emission standard, but decrease under emissions tax

CLevel of emissions decrease under emissions standard, but remain unchanged under emissions tax

DLevel of emission decreases under both approaches