Question

If a body is charged by rubbing it, its weight (a) remains precisely constant

Answer 1

yes it is true that it is constant

Answer 2

If a body is charged by rubbing one is positive and other is negative. So it will depend charged by friction one has less electrons(positive charged body) and other has more number of electrons (negative charged body). Soif it is charge is positive then weightdecreases and vice versa.