The correct option is C Glass rod : positive charge, Silk: negative charge.
On rubbing a glass rod with silk, the electrons from the glass rod get transferred to the silk. The silk now has an excess of electrons and so is negatively-charged. On the other hand, the glass rod is deficient in electrons and hence is positively-charged.
In the above example, the silk undergoes negative electrification.
Hence, silk obtains negative charge and glass retains positive charge.