A、Different types of sandwiches. B、The most popular sandwich in UK. C、The origin of sandwiches. D、The reasons for sandwich’s pop

At lunch time, and sometimes at other times in the day, people in the UK often eat a "sandwich". This consists of two pieces of bread and a filling.
    However, there are literally hundreds of different types of sandwiches, and each variation has its own flavour. Some of the most popular and famous sandwiches in the UK are: BLT, Ploughman’s, Tuna, and Egg sandwiches. Sandwiches of all varieties are extremely popular, and quick and easy to eat. In fact, British people eat 2.8 billion each year—not bad for a population of only 60 million people!
    In 1762 the first written record of the word "sandwich" appeared in the diary of the English author Edward Gibbons, who remembered seeing the wealthiest elite in the country eating "a bit of cold meat" between pieces of bread. Gibbons did not think this was very appropriate behaviour for such men!
    The snack was named after the Fourth Earl of Sandwich. Sandwich was a frequent gambler, and was so addicted to gambling that he would often refuse to stop even to eat meals. To avoid having to stop gambling, the Earl of Sandwich asked the cooks at his gambling club to prepare him a meal consisting of beef between two slices of bread, so that he always had one hand free to play cards and gamble, and his hands wouldn’t become dirty from the meat.
    When other men saw what he was eating, they began to order "the same as Sandwich!", and so the sandwich was born — beginning as a snack for some of the wealthiest men in England! It quickly became popular and widespread as a quick and easy food to eat.
Questions 16 to 18 are based on the passage you have just heard.
16. What is the passage mainly about?
17. How many sandwiches do British people eat each year?
18. What can we learn about the sandwich?