Can some one help

The skeletal system works as a support structure for your body. It gives the body its shape, allows movement, makes blood cells, provides protection for organs so I would say the first choice, hopefully I helped out !:)

When you are making a guess you are forming a hypothesis

Humans can affect weathering and erosion in several ways.  humans cause  increases in acid rain and pollution, which increase the amount of  weathering  agents in the air and water, and then on land.for an easy answer: 1) acid rain2) pollution