Explanation:

- When a government wants to strengthen its currency, it takes action in the foreign exchange market.

- Option 1: Buys foreign currency and sells domestic currency

- This action would weaken the domestic currency by increasing its supply in the market while reducing the foreign currency supply.

- Option 2: Sells foreign currency and sells domestic currency

- Selling both foreign and domestic currency is an unlikely scenario and does not directly affect the objective of strengthening the domestic currency.

- Option 3: Sells foreign currency and buys domestic currency

- Selling foreign currency and buying domestic currency reduces the supply of the domestic currency and increases demand, leading to an appreciation of the domestic currency.

- Option 4: Buys foreign currency and buys domestic currency

- This approach is contradictory as buying domestic currency would typically be combined with selling foreign currency to strengthen it.