Cotton has a higher tendency to attract electrons than human skin. When Kevin pulls his cotton shirt off his body, the electrons get transferred from the to the. So, the shirt becomes charged and Kevin's body becomes charged.

Shirt becomes negatively charged and Kelvin's body becomes positively charged.

Explanation:

An electron is the elementary particle of atom. It has a negative charge of - 1.6 x 10^-19 C.

If a body loses some electrons, it becomes positively charged and if the body gains some electrons then it becomes negatively charged.

According to the question, cotton has higher tendency to attract the electrons, it means it has a tendency to acquire negative charge.

If Kelvin pulls his cotton shirt the electrons get transfer from his body to cotton shirt. It means the cotton shirt acquire a negative charge and the human body acquires a positive charge as it loses electrons.

So, shirt becomes negatively charged and Kelvin's body becomes positively charged.

When kelvin pulls cotton shirt off his body, the electrons get transferred from the shirt in the form of static charges that means electrons to the body. So, the shirt becomes positively charged and his body becomes negatively charged.

So, the transfer of charge from shirt to the body will takes place. And also we can hear a crackling sound. We can hear it and observe it as a sparkle.

Therefore the cotton has higher tendency to attract the electrons than human skin.