Charging By Friction

Which of the following cannot be charged by friction, if held by hand ?

When a body is negatively charged by friction, it means

When two bodies A and B are rubbed, they acquire charge by friction, If the charge on A is negative, then the charge on B is "_______" .

Which of the following are transferred from one object to another when these two objects are charged by friction ?

When a plastic comb is rubbed with dry hair, the hair get positively charged by friction. In this porcess :

Out of sliding friction, static friction and rolling friction : Which one is the smallest ?

Out of sliding friction, static friction and rooling friction : which one is the largest ?

The coefficent of friction mu and the angle of friction lamda are related as