Teacher: And now, children, we are moving to the test part of our class. Who'd like to be the first to hear and answer the questions from the quiz?
Helen: May I, Mrs. Brown?
Teacher: Yes, Helen, you may! OK. Here is the question. How was the geographical position of the current shape of the North American continent?
Helen: It was formed because the great northern ice cap flowed over the North American continent. This ice flow determined the size of the Great Lakes, the direction of the Missouri River and carved the channel of the Hudson River.
Teacher: Good job, Helen! What mountains are there in America?
Helen: If I'm not mistaken, there are the following mountains in America: the Appalachians, the Rocky Mountains, the Cascade Mountains, the Coast Ranges and the Sierra Nevada range.
Teacher: Yes, Helen, you are quite right. And to sum up your quiz questions, which mountains are the oldest among those you've just named?
Helen: The oldest mountains in the United States are the Appalachians.
Teacher: Very good, Helen Wright, You've got 98 points out of 100. Please take your seat.
Helen: Thank you, Mrs. Brown.