Astronomy hAs BEEn A sourCE For myriAD iDEAs inFluEnCing EvEry suBjECt. thE stArs hAvE{{u}} (67) {{/u}}sinCE thE DAwn oF mAn. pEoplE hAvE lookED to thE{{u}} (68) {{/u}}to DEtErminE physiCAl loCAtion in thEEArth, to{{u}} (69) {{/u}}timE AnD to gAin spirituAl DirECtion. in EArly{{u}} (70) {{/u}}oF thEEArth, humAns hAD only thEir FivE sEnsEs to{{u}} (71) {{/u}}thEm. vEnturing out At sEA woulD hAvE BEEn impossiBlE iF pEoplE hAD not rEAlizED thAt thE stArs stAy{{u}} (72) {{/u}}ConstAnt in position. Following thE stArs AllowED mAnkinD to{{u}} (73) {{/u}}thE First systEm For giving DirECtion.An ADvEnturEr CoulD DEtErminE whAt DirECtion thEy wErE FACing AnD gEt A (n){{u}} (74) {{/u}}iDEA ABout how FAr thEy hAD to go. sinCE thE BEginning, thE stArs hAvE BEEn usED not only{{u}} (75) {{/u}}An EFFECtivE tool For pEoplE to{{u}} (76) {{/u}}in BAsiC living But Also to{{u}} (77) {{/u}}unDisCovErED things ABout thE worlD、thE 17thCEntury wAs FillED{{u}} (78) {{/u}}mAny DisCovEriEs Both in Astronomy AnD in mAthEmAtiCs. thE AstronomErs’{{u}} (79) {{/u}}oF thE univErsE throughout thE 17thCEntury wAs rEFErrED to As thE ptolEmAiC systEm. thEy prEsumED thAt All things ArounD thE EArth wErE unChAnging.AnothEr populAr{{u}} (80) {{/u}}wAs thECopErniCAn systEm. this is whErE thE sun is thE CEntEr rAthEr thAn thE EArth. onE oF thE mAin sCiEntists During thE 17thCEntury wAs gAlilEo. hE BEliEvED{{u}} (81) {{/u}}thECopErniCAn systEm. whEn gAlilEo pointED his tElEsCopE to thE sky, hE{{u}} (82) {{/u}}mAny importAnt sCiEntiFiC DisCovEriEs thAt{{u}} (83) {{/u}}thECopErniCAn systEm. hE FounD thAt thE moon wAs not A{{u}} (84) {{/u}}sphErE As thought oF in thE ptolEmAiC systEm; it hAD CrAtErs AnD mountAins not{{u}} (85) {{/u}}to thE humAn EyE. hE Also DisCovErED thAt thE sun hAD spots. thEsE DisCovEriEs All{{u}} (86) {{/u}}thE ptolEmAiC systEm.

A．ExplAnAtion
B．ExplorAtion
C．ExpAnsion
D．ExpEDition