Which one of the following statements related to taxes is correct?

A、Themarginaltaxratemustbeequaltoorlowerthantheaveragetaxrateforafirm.;
B、Thetaxforafirmiscomputedbymultiplyingthefirm'scurrentmarginaltaxratetimesthetaxableincome.;
C、Additionalincomeistaxedatafirm'saveragetaxrate.;
D、Giventhetaxstructurein2014,thehighestaveragecorporatetaxrateis34percent.;
E、Themarginaltaxrateforafirmcanbeeitherhigherthanorthesameastheaveragetaxrate.