Why do scientists think earth's core contains iron?

Which theory suggested that the earth was once a signle supercontient that gradually that broke up into the contients that we know today

How long does it take neptune to orbit the sun?

Afarmer who is grown corn for the past five years notices in the sixth year that the his harvest is significantly smaller, despite an increase in labor on the farm. the following year, the harvest continue to decline. which of the following explanations most plausibly accounts for the reduction in corn yield? a) soil degradation b) desalinization c) better irrigationd) terracing