Which of the following objects is not normally used in current space exploration?
a. space shuttles
c. single use rockets
b. space stations
d. space probes

a).  Space shuttles.
       Yes.  NOT current.
       The last space shuttle flight was in July 2011.

b).  Single-use rockets.
       No.  Current.
       The first successful test of a re-usable booster
       took place just in the last few weeks.
       Currently, EVERYTHING is single-use.

c).  Space stations.
       No.  Current.
       The International Space Station is currently operational.

d).  Space probes.
       No.  Current.