Please answer the following question: Read the following article and select the best answer. Article: After years of research and testing, the hybrid car was developed and put on the market. It's an interesting and exciting new improvement in today's world as we look for better ways to protect the quality of the air we breathe and conserve our natural resources. The quality of our air is affected by many different things. But one of the largest sources of air pollution is the burning of fossil fuels such as coal and gasoline which are used to power a car's engine. The EPA has set national standards to help control the level of harmful pollutants sent off into the air, and the automobile industry has acted by producing a hybrid car that uses less gas and therefore causes less pollution. A hybrid car is a combination of a regular car that runs on gasoline and an electric car that is battery powered. Some people tend to think that since the hybrid car is partially electric, you have to plug it in to charge it. But that's not how it works. The 144 volt battery pack is actually recharged( ) through the energy that is produced when the car's brakes are used. This is referred to as "regenerative braking", because it generates electricity. Although the hybrid car still runs on gasoline most of the time, this helps it use less gas than a regular car. When the driver stops at a traffic light, the engine automatically ( ; )shuts off to save fuel. Then, as soon as the driver puts the car in gear and touches the gas pedal, the engine starts back up. Have you ever ridden in a car with someone who ran out of gas? That probably wouldn't happen if you were riding in a hybrid car. It flashes a warning on its computer screen that says, "I am low on gas". When it completely runs out, the warning reads, "YOU ARE NOW OUT OF GAS!" Then the electric power supply kicks in to let the driver travel a few more miles to a gas station. Question: According to the passage, the word "hybrid" refers to _ . - a high tech discovery - energy saving - a new invention - a combination of two things
Answer:
a combination of two things