The going concern assumption is concerned with

a. The company's ability to continue operations long enough to carry out its existing obligations.
b. Measuring ongoing business activities at their exchange price at the time of the initial external transaction.
c. offsetting management's natural optimism by providing a prudent approach to uncertainty in financial statement items.
d. Any information that is capable of influencing the decisions of anyone using the financial statements.

The correct answer is a. The going concern assumption is concerned with the company's ability to continue operations long enough to carry out its existing obligations.

To arrive at this answer, you may consider the following process:

1. Understand the concept: The going concern assumption in accounting assumes that a company will continue to operate in the foreseeable future. This assumption is fundamental to financial reporting and impacts the preparation of financial statements.

2. Evaluate the options:

a. The company's ability to continue operations long enough to carry out its existing obligations: This option aligns with the definition and concept of the going concern assumption.

b. Measuring ongoing business activities at their exchange price at the time of the initial external transaction: This option seems to relate to the concept of historical cost or fair value measurement, not specifically the going concern assumption.

c. Offsetting management's natural optimism by providing a prudent approach to uncertainty in financial statement items: This option focuses on the concept of conservatism in accounting but does not directly address the going concern assumption.

d. Any information that is capable of influencing the decisions of anyone using the financial statements: This option seems to relate to the concept of materiality or relevance, but it doesn't directly address the going concern assumption.

3. Select the most appropriate answer: Based on the evaluation, option a, which refers to the company's ability to continue operations long enough to carry out its existing obligations, aligns with the going concern assumption.

Therefore, the correct answer is a. The going concern assumption is concerned with the company's ability to continue operations long enough to carry out its existing obligations.