Unit5TextPioneersofFlight课文练习:,,,manyofitsdesignfeatureshavebeenincorporatedintotoday’,,,:’sdesigns/sketches重点句理解:.(),whichYangLiweihadprobablydreamed/cherishedwhenhewasmuchyounger,-fetched,theprinciplesofrocket-poweredspaceflightarecontained