概括大意和完成句子(第23~30题，每题1分，共8分)
下面的短文后有2项测试任务：(1)第23~26题要求从所给的6个选项中为指定段落每段选择1个小标题;(2)第27~30题要求从所给的6个选项中为每个句子确定一个最佳选项。
LearnaboutLight
1 Ancientcivilizationswereamazedbytheexistenceoflightforthousandsofyears. TheGreekphilosophersbelievedthatlightwasmadeupofcountless, tinyparticlesthatenterthehumaneyeandcreatewhatwecallvision. However, EmpedoclesandaDutchscientistnamedChristianHuygensbelievedthatlightwaslikeawave. Accordingtothem, lightspreadoutandtravelledlikeastraightline. Thistheorywasacceptedduringthe 19thcentury.
2 ln 1905, AlbertEinsteinpublishedaresearchpaperinwhichheexplainedwhatisreferredtoasthephotoelectriceffect. Thistheoryexplainsthatparticlesmakeuplight. TheparticlesEinsteinwasreferringtoareweightlessbundles(束)ofelectromagnetic(电磁)energycalledphotons(光子). Today, scientistsagreethatlighthasadual(二重) natureitispartparticleandpartwave. Itisaformofenergythatallowsustoseethingsaroundus.
3 Thingsthatgiveofflightareknownassourcesoflight. Duringtheday, theprimarysourceoflightisthesun. Othersourcesoflightincludestars, flames, flashlights, streetlampsandglowinggasesinglasstube.
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