There was once a farmer who had a fine olive orchard. He was very hardworking, and the farm always prospered under his care. But he knew that his three sons despised the farm work, and were eager to make wealth, through adventure. When the farmer was old, and felt that his time had come to die, he called the three sons to him and said, "My sons, there is a pot of gold hidden in the olive orchard. Dig for it, if you wish it." The sons tried to get him to tell them in what part of the orchard the gold was hidden, but he would tell them nothing more. After the farmer was dead, the sons went to work to find the pot of gold. Since they did not know where the hiding-place was, they agreed to begin in a line, at one end of the orchard, and to dig until one of them should find the money. They dug until they had turned up the soil from one end of the orchard to the other, round the tree-roots and between them. But no pot of gold was to be found. It seemed as if someone must have stolen it, or as if the farmer had been wandering in his wits. The three sons were bitterly disappointed to have all their work for nothing. The next olive season, the olive trees in the orchard bore more fruit than they had ever given. When it was sold, it gave the sons a whole pot of gold. And when they saw how much money had come from the orchard, they suddenly understood what the wise father had meant when he said, "There is gold hidden in the orchard. Dig for it, if you wish it." The farmer told his sons about the pot of gold because   _  .
his sons were very hardworking his sons would take the adventure his life would come to an end he couldn't keep the secret