PLEASE HELP! A sample of radioactive waste will have reached an acceptable activity level at 0.5 curies . If the half - life of the sample is 5 years and the sample can be disposed of after a minimum of 20 years , what must the original activity level of the sample be ?

Which would best keep the oxygen cycle stable? a. cutting down jungles to create farmland b. eliminating parks in large cities c. dumping toxic chemicals into the ocean d. reducing the amount of deforestation d. reducing the amount of deforestation

Osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. what really drives osmosis? view available hint(s)osmosis is often viewed incorrectly as a process driven directly by differences in solute concentration across a selectively permeable membrane. what really drives osmosis? the first law of thermodynamicsthe difference in the height of water columns on either side of a selectively permeable membranethe difference in water concentration across a selectively permeable membranethe difference in sugar or ion concentration across a selectively permeable membrane

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?