What does Mary think is so incredible and wonderfu

单项选择题

SECTION A CONVERSATIONS In this section you will hear several conversations. Listen to the conversations carefully and then answer the questions that follow. Questions 1 to 3 are based on the following conversation. At the end of the conversation, you will be given 15 seconds to answer the questions. Now listen to the conversation.

What does Mary think is so incredible and wonderful

A．The speed of light.
B．The speed of telecommunication.
C．Astronauts landing on the moon.
D．The United States.