Can someone answer all of the questions?

Examine the equation. 23490th→23088ra+42he what kind of barrier would you need to block the radioactive particles from this reaction? a.a piece of paper b.a sheet of aluminum foil c. a two-inch block of lead d. a solid concrete block

Does anyone know how to solve this problem? i really need . i made an attempt but i just cant get it. a metal rod is 25.000 cm long at 25.0 degrees celsius. when heated to 102.0 degrees celsius, it is 25.054 cm long. what is the coefficient of linear expansion for this metal.

Smallest intensity of a stimulus that you can detect 50 percent of the time is