1. What is the best description of the CMB? A. Energy from the Sun measured in microwaves B. The chemical composition of hydrogen and helium C. Residual energy leftover from the origin of the universe D. Evidence that galaxies are rapidly moving apart 2. How do scientists study light from 14 million miles away? A. Wavelengths using the electromagnetic spectrum B. Temperature using a thermometer C. Chemical composition using a microscope D. Reflection of light using a mirror 3. Microwaves from the CMB are considered to be the __ in the universe. A. Lowest frequency B. Highest frequency C. Newest D. Oldest

## Step1<br />The Cosmic Microwave Background (CMB) is the residual heat leftover from the Big Bang, which occurred approximately 13.8 billion years ago. This makes option C the correct answer for the first question.<br /><br />## Step2<br />Scientists study light from distant stars and galaxies using the electromagnetic spectrum. This spectrum includes all types of electromagnetic radiation, including light. By analyzing the wavelengths of this light, scientists can determine various properties of the light source, such as its temperature and chemical composition. Therefore, option A is the correct answer for the second question.<br /><br />## Step3<br />The CMB is the oldest light in the universe, dating back to the time of the Big Bang. Its microwaves are the oldest in the universe, having traveled through space for about 13.8 billion years. This makes option D the correct answer for the third question.