Themegaphone(microphone)makesthevoicesoundlouderbecauseitpointssoundwavesinonedirectionandkeepsthemfromspreadingoutinalldirections.
A、slitheringThe fear of smallpox, which terrorized the eighteenth century, has no analogy(likeness) today.
Double Eagle in the first transatlantic balloon, was greeted by avid crowds in France.
Someseaurchins海膽havevenomous(toxin)spines
The wheels of the first road vehicles were fashioned from crude stone disks.
The Native American interpreter Sacajawea was a valuable member of the Lewis and dark expedition in 1805.
