Final answer:
The adjustment entry for recording interest on capital under the fixed capital method is to debit Interest on Capital and credit Capital. Therefore, the correct option is B.
Step-by-step explanation:
The correct adjustment entry for recording interest on capital when the capital account is maintained under the fixed capital method is:
b. Debit Interest on Capital, Credit Capital
This entry increases the Interest on Capital account and decreases the Capital account, reflecting the allocation of interest earned on the capital investment.