Stapes foot plate covers -: (A) Round window, (B) Oval window, (C) Inferior sinus tympani, (D) Pyramid
Answer is B. Footplate of stapes covers the oval window and secondary tympanic membrane covers the round window.
Mnemonic : SORT : 

* Stapes (footplate) covers 
  Oval window
*Round window is covered by
 Tympanic membrane (Secondary)