2. If the unstable atoms in a rock have a half-life of 2 million years and the rock begins with 8 mg of unstable atoms, how many milligrams of unstable atoms will be found in the rock 4 million years
after its formation?

cuz he's blad

explanation:

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.