The article discusses three ways to make companies reduce greenhouse gas emissions: carbon taxes, cap-and-trade, and a mix of both. It explains that when the negative effects on business are low, a tax is best, but when the effects are high, a mix or cap-and-trade is better. A tax makes prices clear and can earn money, while cap-and-trade can prevent businesses from moving elsewhere to pollute. A mix of the two seems to be the most effective in reducing emissions and protecting businesses. The article mentions British Columbia uses a tax, and Quebec uses cap-and-trade.