Many science graduates prefer to work in the pharmaceutical industry because they can be better paid in the pharmaceutical industry than in the lab work.

A．Current rockets are vulnerable and unstable.
B．New propulsion system has been developed.
C．People consider laser beams as a possible solution to developing new propulsion system.
D．At present, nuclear energies can be used in propulsion systems.

A．the development of space' technology
B．the obstacles and prospects of space transportation
C．the public interests in space travel
D．the growth of space business