Explain the reason with the story.

1. Robinson saved Friday. After seeing the brutal scene of savage cannibalism, Robinson reinforced his "wall" and lived in a secluded place. At the same time, he also had the idea of killing savages. Soon after, he once again saw a group of savages coming to the island to hold a feast of human flesh, and one of the "captured" savages escaped from the crowd ready to eat him. Robinson decisively stepped in to help the fleeing savage, killed two pursuers and rescued the savage. Robinson regarded him as his slave and named him "Friday". Under Robinson's instruction, "Friday" quickly learned to dress, shoot, speak English and believe in Christ … and became Robinson's most loyal servant and friend. 2. out of the need of life, Robinson began to make pottery. After finding the clay, he did countless experiments. At first, some clay was not finished because it was too soft, and some exploded because the temperature was too high. After groping for more than two months, I finally made two large pottery vessels and many small ones, but there is still no pottery jar that can hold liquid and stand the fire. By chance, I found that some broken pottery utensils were burned as hard as stones, so Robinson began to study the firepower of burning pottery, and finally burned three pottery pots and two pottery pots, one of which was exactly what Robinson needed. Robinson built a canoe. In order to cross the island to reach the mainland, Robinson wants to build a canoe like the aborigines. Being in a hurry to deliver the goods, he didn't think much when he started working. As a result, the wooden boat that took several months to cut out from the cypress was abandoned because it was too big. A few years later, Robinson learned his lesson, dug a smaller canoe along the river, put on a mast and sails, and cut many slots to put things on the boat. But because the wooden boat is too small, Robinson can't take it to the opposite mainland, so he can only use it nearby. +1 praised related knowledge.