Which of the following options should replace the underlined word in line 4?

Directions: Read the following passage and answer the given question.

1. A farmer had three sons who were idlers.

2. When the farmer fell ill, he told them that ______________.

3. Before the farmer died, the sons went to the field and dug the whole field but found no treasure.

4. Then they understood the real meaning of his father’s advice.