Which gas law has the assumptions of a fixed amount and temperature of a gas?

The parameters taken into account in gas laws are pressure, temperature, volume and amount.Gas laws find the relationships between any 2 parameters keeping the remaining parameters at constant. 
In this case, the parameters that are fixed are temperature and fixed amount. This means that the gas law is Boyle's law.
Boyle's law states that pressure of gas is inversely proportional to volume of the  gas at constant temperature and fixed amount.
PV = k 
where P - pressure, V - volume and k - constant 
Correct answer is therefore Boyle's law.

Alpha particles have positive charge, beta particles have negative charge, and answer 4 just doesn’t make sense. thus, you are left with only one possible answer.