Reply																		
							Sat 12 Dec, 2015 01:50 pm
						
						
					
					
					
						Many years ago, my non-native teacher marked my essay, and he added of in the blank:
- This was __  a critical time for their country.
I don't understand why he did that, because I would think my sentence is fine, and nothing should be used in the blank. Why did he insert of?
					
				 
				
						
														
					
													@WBYeats,
												Because, WB, "of" implies a third subject doubtless described in the context, the subject of "This."  Billy Thornton had written an essay describing a notable period, in which many at that time had been personally affected.  His essay, then was 
of a critical juncture in their existence