What's the author's tone in the last sentence of the passage

A．Take Vacations in Space
B．Building Hotels in Space
C．Flight regulations in Space Travels
D．Cost of Space Traveling

A．The biggest hurdle for the space - tourism project is lack of a life supporting system.
B．The entrepreneurs trying to explore the space - tourism have plenty of money.
C．The government have little interest in this project.
D．The first passenger countdowns are within a few years.