A team of engineers is designing a habitat for astronauts to live in on the Moon. Which statement describes a criterion of this project?
A. The habitat must cost less than $700,000 per year to maintain.
B. The habitat must have an airlock that lets astronauts out onto the
Moon's surface.
C. The habitat must be built entirely from materials brought from
Earth.
D. The habitat must use fewer than 200,000 kg of materials.