Answer:
The correct answer is **D. Burn them and see how hot they can make a water sample**.
Step-by-step explanation:
Here's why: 1. Efficiency of energy sources: Scientists compare the efficiency of different energy sources to determine how effectively they can convert their stored energy into useful work or heat. 2. Burning and heat: When energy sources such as fuels are burned, they release energy in the form of heat. By measuring the amount of heat produced, scientists can compare the efficiency of different energy sources. 3. Water as a reference: Water is commonly used as a reference substance because it has a known heat capacity. By measuring how hot a water sample gets when exposed to the energy released from burning an energy source, scientists can compare the efficiency of different sources. 4. Controlled experiments: Scientists conduct controlled experiments where they burn different energy sources and measure the resulting increase in temperature of a water sample. By comparing the temperature changes, they can assess the relative efficiency of the energy sources. In summary, scientists compare the efficiency of different energy sources by burning them and measuring how hot they can make a water sample. This allows them to determine how effectively the energy sources can convert their stored energy into heat, providing insights into their relative efficiency.