Final answer:
The exchange rate regime in the described scenario is a floating exchange rate.
Step-by-step explanation:
The exchange rate regime described in the question is a floating exchange rate. In a floating exchange rate system, the value of a country's currency is determined by the foreign exchange market and can fluctuate freely.
In this scenario, country A's currency is floating, which means its value is determined by market forces. Country B's exchange rate is fixed to country A's currency, which means the value of country B's currency is kept at a constant rate relative to country A's currency. However, since country B does not restrict the flow of capital in and out of the country, this indicates that there is no government intervention or control over the exchange rate.
Therefore, the correct answer is B. Floating exchange rate.