Question 1
A drinking straw attracts small pieces of paper after it is rubbed with a cotton cloth, but not before. Why?
The right answer is the one marked above.
Static electric charges have arisen on its surface. Rubbing gives the straw an attractive force, and it gets that force from the static charges the rubbing produces.
The unrubbed straw is the control. Same object, same shape, same weight — only the rubbing is missing, and only the attraction is missing with it.