Which of the following statements about GDP is correct?

• Nominal GDP values production at constant prices, whereas real GDP values production at current prices.
• Nominal GDP values production at market prices, whereas real GDP values production at the cost of the resources used in the production process.
• Nominal GDP consistently underestimates the value of production, whereas real GDP consistently overestimates the value of production.
• Nominal GDP values production at current prices, whereas real GDP values production at constant prices.