The invention of the internal combustion engine allowed which advancement?
a. light bulb
b. steamships
c. airplanes

Which factors add to the greenhouse effect and are caused by human activities?

¿cual es mas alta en baja california, la migracion o la inmigracion?

One of the main reasons societies settled along rivers in the neolithic era was because a) the village elders demanded it. b) the land there was more valuable. c) it was more safe and secure there. d) it provided irrigation for farming.