What does this symbol mean, and which safety precaution must be taken when it is present?

Which of the following correctly list the first appearance of organism in the fossil record from earliest to most recent

Consider the last statement in the prompt: "people take such environmental factors into account in their choices when deciding where to live." do all people have a choice as to where they live? what factor plays a key role in this decision and may therefore play a large role in determining quality of life?

Which equation is used to calculate the magnetic force on a charge moving in a magnetic field