Read the text and answer questions 11 to 14.
 

    Once upon a time, there was a handsome man. His name was Batara Guru Sahala. He liked fishing. One day, he caught a fish. He was surprised to find out that the fish could talk. The fish begged him to set it free.

    Batara Guru could not bear it. He made the fish free. As soon as it was free, the fish changed into a very beautiful woman. Batara Guru was attracted to her. He felt in love with that fish-woman. He wanted to marry her. The woman agreed with one condition: Batara Guru had to keep the secret that she had been a fish. Batara Guru agreed and promised that he would never tell anybody about it.

    They got married happily. They had two daughters. One day, Batara Guru got very angry with his daughters. He could not control his anger. He shouted angrily and got the word of fish to his daughters. The daughters were crying. They ran to their mother and told her about it.

    The mother was very upset. Batara Guru broke his promise. The mother then shouted so angrily that the earth began to shake. Volcanoes started to erupt. The earth formed a very big hole. People believed that the big hole became a lake. Then this lake is known as Toba lake.

Adapted from: http//britishcourse.com/the-legend-of-toba-lake-legend-narrative-text.php

Why did the mother feel very upset?