Final answer:
A partner's capital account is credited when they make additional or original investments, and when profits are allocated, but not credited for the debit balance of their drawing account. Option a.
Step-by-step explanation:
The partner's capital account is credited in several instances that reflect an increase in the owner's equity in the business. These instances include when the partner makes an additional investment option a, to the partnership, which is an injection of further capital, and when the partner's original investment is recorded, establishing their initial stake in the partnership. A credit is also appropriate when recording the partner's share of profit, as earnings are distributed in accordance with the partnership agreement. However, the partner's capital account is not credited when recording the debit balance of the partner's drawing account at the end of the period, instead, this drawing account would typically be debited to reflect the withdrawal of funds from the business by the partner.