Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions.
As any student can tell you, sometimes it takes a lot of work and effort to commit information to memory before a big exam. However, some other events, details, and experiences enter our memory with little or no effort. For example, you might hear a catchy song on the radio once and still remember its tune days or weeks later. So why does it seem like some things are so difficult to remember and other things so easy? What's the difference?
When you're trying to intentionally remember something (like a formula for your statistics class or a list of dates for your history class), this information is stored in your explicit memory. People use these memories every day, from remembering information for a test to recalling the date and time of a doctor's appointment. There are two types of explicit memory: episodic memory, which is your long-term memories of specific events, like what you did yesterday or your high school graduation, and semantic memory, which is memories of facts, concepts, names, and other general knowledge.
Things that people don't have to purposely try to remember are stored in implicit memory. This kind of memory is both unconscious and unintentional. Some examples of implicit memory include singing a familiar song, typing on your computer keyboard, and brushing your teeth. Riding a bike is another example. Even after going years without riding one, most people who have already learned how to ride a bike are able to hop on and ride it effortlessly without thinking consciously.
These two major types of memory play important roles in shaping your ability to recall pieces of information and interact with things in your environment. Knowing some of the major differences between them is important for understanding how memory works.
(Adapted from verywellmind.com)

Question 39: What is the passage mainly about?
A. The role of explicit and implicit memory B. The different types of memory
C. Episodic memory and semantic memory D. How to have a better memory