Correct option is D
 The correct option to fill in the blank is (d) 
  pane.
  
  
  Explanation: 
  Pane means a 
  single sheet of glass in a window or door—exactly what a carpenter would replace. 
  (Hindi: काँच की पट्टी/परत). 
  
  
  Example: 
  The storm shattered one  
   pane  
   of the French window. 
  
  
  Why other options are incorrect: 
  
 · 
  (a) plain: simple/without decoration; not a glass sheet. 
  (Hindi: सादा/समतल). 
  
 · 
  (b) peyn: non-standard/incorrect spelling; not an English word.
  
 · 
  (c) pain: physical or emotional suffering; irrelevant here. 
  (Hindi: दर्द).