Astronomical means related to Astronomy. Astronomy is the study of the Universe. Because some large numbers are used there, the word "astronomical" is also popularly used for large numbers in general.
It means "related to Astronomy".
Also, since some very large numbers are used in Astronomy, especially for distances, "astronomical" is also used (in popular speech) in the sense of "huge,...
It means "of, pertaining to, or connected with astronomy" (the study of stars).The idiomatic meaning of "huge," "having a high numerical value," or "exorbitant" (as in astronomical prices) came about...
Tubas, trombones, and trumpets are not astronomical instruments. A clarinet could be if you put some lenses in it.
ProTip: include the multiple choice answers along with the multiple choice...