The astronomical database tracks the observations made by astronomers, including the date, time, location, and type of object observed. The database stores data about the astronomers, telescopes, and celestial objects. This database looked after by a space exploration agency tracks spacecraft data, including launch dates, mission objectives, and current status. The database also stores data about the spacecraft, missions, and launch sites.

For the above database problem statement, which of the following is NOT correct?

Question $5$ options:

Entities: celestial$\_$objects

Primary key: celestial$\_$object$\_$identifier

Attributes: astronomers, agency

Relationship: observe