Final answer:
Class 50 has the highest CCA rate applied to the UCC balance among the options provided, with a rate of 55% (A). Class 12 includes assets like tools and certain equipment but applies on a different basis. Class 10 and Class 1 have lower CCA rates of 30% and 4%, respectively.
Step-by-step explanation:
The question concerns the calculation of Capital Cost Allowance (CCA) rates for different asset classes in Canada. The highest rate applied to the UCC balance when computing CCA among the options provided is for Class 50, which typically includes certain types of manufacturing and processing machinery and equipment.
The CCA rate for Class 50 assets is 55%. In contrast, Class 12 includes assets with a CCA rate of 100%, but it applies to a different basis and not to the UCC balance. Class 10 has a 30% rate and Class 1 has a lower rate of 4%. Thus, out of the options listed, Class 50 has the highest CCA rate applied to the UCC balance.