Trains are a popular mode of transportation that are used to carry a variety of things. The correct answer to the question is option 'A', which states that trains carry passengers and mail. Let's explore this answer in detail.

Passengers:
- One of the main purposes of trains is to transport passengers from one place to another. Trains have specially designed compartments or cars that are equipped with seats or berths to accommodate passengers during their journey.
- Passengers can travel on trains for various reasons such as commuting to work, going on vacations, visiting family and friends, or attending events in different cities.
- Trains provide a comfortable and convenient way for people to travel long distances without the need for driving or dealing with traffic. They offer amenities such as restrooms, snack bars, and sometimes even sleeping arrangements for overnight trips.

Mail:
- Trains also play a significant role in transporting mail and parcels from one location to another. They have designated compartments or cars that are specifically designed to carry mail.
- The mail is usually organized and sorted before being loaded onto the train. It is then transported to different destinations, where it is further sorted and delivered to its final recipients.
- Train transportation is often used for long-distance mail delivery, as it is efficient and cost-effective for carrying large volumes of mail over extended distances.

Other types of cargo:
- While the primary focus of trains is on carrying passengers and mail, they can also transport other types of cargo. Trains have freight cars that are specifically designed to carry goods and materials.
- Freight trains can transport a wide range of items such as raw materials, finished products, machinery, vehicles, and even livestock. These goods are often loaded onto the train in containers or specialized wagons for safe and efficient transportation.
- Freight trains are an essential part of the logistics industry, providing a reliable and economical means of transporting goods over long distances.

In conclusion, trains carry a variety of things including passengers and mail. They are an important mode of transportation for both people and goods, offering a convenient and efficient way to travel and transport items over long distances.