What energy transfer is occurring when a battery powered toy rolls across the floor ?

Noble gases is far right

Combustion is the act or process of burning. therefore, i believe the answer is  a: burning wood. 

Using dilution equationm1v1 =m2v2 ; where m1 and m1 are the intiial and final concentration, and v1 and v2 are the initial and final volume.5  × 5 m = 8 l  × m2m2 = 25/8 = 3.125 mtherefore; the resulting molarity is 3.125 m