A、Separate houses were built for storing ice. B、Double walls were built in icehouses to keep cool. C、Blocks of ice were packed w

Years ago before there were refrigerators, an ice-house was a building used for storing ice. The first icehouses were in the cellars of farmhouses. Pieces of ice, mixed with snow and meadow grass, were piled in winter and kept until the following summer. Soon farmers began to build separate houses for storing ice. These icehouses had double walls with hay stuffed between to keep out any heat. Blocks of ice were put inside the icehouse and packed with straw or sawdust.
    Where did the ice for these icehouses come from? Workers took it from a frozen pond or river. They sawed the ice into even blocks. Then they pulled the ice blocks from the water with hooks and carried them to the icehouses on sleds. Special tools helped the workers cut and handle the ice. Ice axes chopped large holes in the ice. Ice saws cut the ice into even blocks. Choppers loosened these blocks from one another. Ice hooks fastened themselves into the large blocks. Then they could be carried over the frozen surface of the pond or river. Tongs were used to pick up the smaller blocks of ice. Ships carried ice all over the world. In 1799 the first boatload in the United States was sent from New York City to icehouses in New Orleans, Louisiana. A boatload was sent from Boston, Massachusetts, to the West Indies to help fight yellow fever in 1805. Ice merchants in Boston also shipped tons of ice from ponds and rivers to cities in Europe.
Questions 19 to 21 are based on the passage you have just heard.
19. Which of he following is NOT mentioned as a step for farmers to store ice in icehouses?
20. Which of the following is NOT true?
21. Which of the following is the correct order in which workers cut and handle ice?