Answer the following question given this paragraph: 

Based on their knowledge of subatomic particles, scientists have developed a theory called the standard model to explain all the matter in the universe and how it is held together. The model includes only the fundamental particles in the Table above . No other particles are needed to explain all kinds of matter. According to the model, all known matter consists of quarks and leptons that interact by exchanging bosons, which transmit fundamental forces. The standard model is a good theory because all of its predictions have been verified by experimental data. However, the model doesn’t explain everything, including the force of gravity and why matter has mass. Scientists continue to search for evidence that will allow them to explain these aspects of force and matter as well. You can learn much more about the standard model at the URL below. Click on “the standard model” and follow the sequence titled “What is fundamental?”.


Q: What is the theory scientists use to explain the matter in the universe and how it's held together?

 Choices:

- specific model

- original model

- organic model

- standard model

A:
standard model
