i hope this with your question .
acceleration has the dimensions of velocity (l/t) divided by time, i.e. l.t−2. the si unit of acceleration is the metre per second squared (m s−2); or "metre per second per second", as the velocity in metres per second changes by the acceleration value, every second.
uranium-238 i believe is your answer
the answer is c because material is worn away because of weathering>
mineral dusts are solid particles, that may become airborne depending upon their origin and the surrounding physical conditions. lead is potential poison. it is obtained from the earth crust. the lead poisoning is a popular occupational hazard. the lead in air, when taken by the human body through respiration is responsible to cause anemia, weakness and kidney and brain damage, labored breathing and lung diseases.