Scientists have many problems that they are working on but are unable to reach a useful solution. There are a number of constraints that can make problems unable to have a solution. Match the current scientific problem and the major constraint to finding a solution.

well , a current problem as you know is covld 19. scientist struggle to find a cure or solution to this because we don't know enough about it because the disease or illness developed so recently. because we don,t know enough about it, we don't have the needed knowledge to finding a solution. We don,t know the DNA/RNA stands in this virus, we don't know how it spreads so fast, how it can infect animals and humans as we don,t have similar DNA strands except for monkeys but dogs have been infected with the virus. it simply because of the unknown. hope this helps as an example!

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong

dynamic equilibrium is the answer.