Which of these statements is true? O a. None of these statements are true. O b. When comparing economies, only Gross National Happiness is measured by all countries, including the Kingdom of Bhutan, and therefore this should be the measure used. O c. When comparing economies, GDP figures are adjusted to account for the proportion of transactions taking place in the informal sector. O d. When comparing economies, an economy such as Peru, which has a large shadow economy, will have overinflated GDP values relative to an economy with a small shadow economy. O e. When comparing economies, the PPP exchange rate should be used so that non-market transactions are accounted for in the value of GDP