You are building a uniform to protect workers from all types of nuclear radiation. if you use material that blocks radiation, then it will probably protect against the other two types.
a. gamma
b. half-life
c. beta
d. alpha

If a material blocks gamma radiation, then it will probably protect against alpha and beta radiation. Alpha particles are large and slow-moving, thus having very little penetrating power. Beta particles are fast-moving, and can penetrate the human flesh up to 1 or 2 centimeters. Gamma particles, however, have great penetration and can easily pass through the human flesh.

Is there any opitions? if you have the periodic table, the noble gases are 8a family, the halogen are the 7a family, and the nonmetal are  carbon, nitrogen, phosphorus, oxygen, sulfur, selenium, fluorine, chlorine, bromine, iodine and astatine.

Answer(a)   the matererials that are in contact, the two materials and the nature of their surfaces/// (b)/// the force pushing the two surfaces together, pushing the surfaces together causes the more of the asperities to come together and increases the surface area in contact with each other