Assertion: HCO3^- can act as a Bronsted acid or Bronsted base. Reason: HCO3^- can donate a proton to form CO3^2- or accept a proton to form H2CO3. A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion. B. Both Assertion and Reason are correct and Reason is not the correct explanation for Assertion. C. Assertion is correct but reason is incorrect. D. Both Assertion and Reason are incorrect.

To solve this question, let's first understand the concepts of a Bronsted acid and a Bronsted base:

- **Bronsted Acid:** A species that can donate a proton (H⁺).
- **Bronsted Base:** A species that can accept a proton (H⁺).

### Assertion:
\[ HC{O_3}^- \] (bicarbonate ion) can act as a Bronsted acid or Bronsted base.

- As a **Bronsted acid**, \[ HC{O_3}^- \] can donate a proton (H⁺) to form \[ C{O_3}^{2-} \] (carbonate ion):
\[
HC{O_3}^- \rightarrow C{O_3}^{2-} + H^+
\]

- As a **Bronsted base**, \[ HC{O_3}^- \] can accept a proton (H⁺) to form \[ {H_2}CO_3 \] (carbonic acid):
\[
HC{O_3}^- + H^+ \rightarrow H_2CO_3
\]

So, the assertion is correct because \[ HC{O_3}^- \] can act both as a Bronsted acid and a Bronsted base.

### Reason:
\[ HC{O_3}^- \] can donate a proton to form \[ C{O_3}^{2-} \] or accept a proton to form \[ {H_2}CO_3 \].

This statement explains why \[ HC{O_3}^- \] can act as both a Bronsted acid and a Bronsted base. Hence, the reason is also correct and it directly explains the assertion.

### Conclusion:
Both the assertion and reason are correct, and the reason is the correct explanation for the assertion.

**Answer: (A) Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.**