Ireally don't understand biology someone me

Which of the following are causes of coastal erosion? check all that apply. beach grasses and other plants trap windblown sand. wave action carves away the coastline. groundwater under pressure is forced to earth’s surface. artificial structures stop the natural flow of sand along the coast. underground caves collapse as bedrock is dissolved.

There are fewer than 100 naturally occurring elements in the universe, but there are millions of different unified substances. explain how this can be true.

When fossil fuels are burned, carbon dioxide is released. how does this gas impact the environment?