A400-gram sample of a radioactive nuclide is left to decay for 30 hours. at the end of 30 hours, only 200 grams of the sample is left. what is the half-life of the nuclide sample

a) 10 hours
b)1.5 days
c) 30 hours
d) 0.5 hours

Which of the following is likely not involved in this example of ecological succession? a) the rotting remains of plants add to the fertility of the soil. b)the soil becomes so fertile that eel grass is replaced by other plant species. c) the roots from plants stabilize the sediment, keeping it in place. d) the concentration of salt becomes so high that all plant life is destroyed.