Please help if you could! Thank you :D

Of the ones listed here, the factor that had the greatest impact on the eventual destruction of native americans' ways of life was the development of the a) automobile. b) highway. c) railroad. d) steamboat.

Atriangle has a side lengths of 18cm, 80 cm and 81cm. classify it as acute obtuse or right?

With alll of except for the 2 that i did already