Themegaphone(microphone)makesthevoicesoundlouderbecauseitpointssoundwavesinonedirectionandkeepsthemfromspreadingoutinalldirections.
A、slitheringSome animals pant and sweat to speed evaporation of body moisture and thus cool themselves.
Eyespots, the most rudimentary eyes, are found in protozoan原生动物 flagellates 鞭毛虫 , flatworms 扁形虫 , and segmented worms片段 蠕虫 .
The company issues an annual report every March.
ThefirstimportantexpositionintheUnitedStateswasheldinPhiladelphiain1876.
When carbon is added to iron in the proper proportions , the result is steel.
