The answer is C) there are guidelines for the strict discomfort of animals
Well land locked countries will not be able to travel farther places quicker. Also they cant ship any thing over seas so trade.
If the half-life is 5 minutes, then 30 minutes is equivalent to 6 half-lives. So, after six successive half-lives, the 400 mg of the radioisotope would have a mass of 400(0.5)⁶ = 6.25 mg.
Thus, A would be the correct answer choice here.