Why are people often surprised when a volcano erupts?

Because there isn't a long warning, they sometimes happen while people are sleeping, and the ground starts shaking and you see lava flowing out of a volcano which is pretty rare

It is really difficult to provide reliable predictions of when it's going to erupt, is the right answer.

Explanation:

A volcano is a break in the outside of a planetary-mass thing, for instance, Earth, that concedes boiling lava, volcanic ash, and fumes to flee from a magma body underneath the exterior.

The volcanoes of the Earth occur because the crust of the earth is split into 17 major, rigorous tectonic bases that glide on a boiling, fainter sheet in its mantle. The most important reason why people often get surprised when a volcano erupts is that it is really difficult to provide reliable predictions of when it's going to erupt.

while it was true that the cotton gin reduced the labor of removing seeds, it did not reduce the need for slaves to grow and pick the cotton.

explanation:

before eli whitney's invention of the cotton gin, picking and cleaning cotton was a slow, labor-intensive job. workers, usually slaves, had to pick the seeds from the cotton fibers by hand. this invention made it possible to grow large amounts of cotton on big farms and make money.

they became hereditary because there weren't many jobs for people in lower classes