The correct answer is option 4, that is, a fewer number of particles of the sample will dissolve in 1 minute.
This is mainly because usually the solubility and the rate of solubility of the salts in water enhances with the increase in temperature, that is, the more the temperature, the faster and higher will be the number of particles that the water can dissolve. Therefore, at 70 degree Celsius more particles will get dissolved in water in 1 minute than at 20 degree Celsius.