Urbanrenewalprogramsstrivetoupgradeareasthatarebecomingslums.

Blue－greenalgaegrowabundantlyinsaltmarshes.

Despitetheproliferationofotherfastermodesoftransportation,therailroadsremainthelargestcarriersofintercityfreightintheUnitedStates.

Themegaphone(microphone)makesthevoicesoundlouderbecauseitpointssoundwavesinonedirectionandkeepsthemfromspreadingoutinalldirections.

In1861itseemedinevitablethattheSouthernstateswouldbreakawayfromtheUnion.