What happens to electric charge during friction

Charging by friction. When insulating materials rub against each other, they may become electrically charged . Electrons , which are negatively charged, may be 'rubbed off' one material and on to the other. The material that gains electrons becomes negatively charged.

i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)

i'm assuming that the correct answer is indeed the first one/ "a"..