Fill in the Blanks Building BridgesOnline version NBB6 - Unit 7 by Tihana Svoren Kolarec 1 connect America long wood easy river Bridges are an important invention ; they places and people . A bridge can be built over a , a stream , a valley , a canyon , a road etc . It can be made of , stone , brick or iron . Today we usually build bridges using concrete and steel . Building bridges is not an job . The first bridges were made of tree trunks or stones . In South , the Inca people made rope bridges . Those were a simple type of today's bridges . The real time for bridges was the 19th century , when people started using steel and concrete , so they could make bridges .
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