Not all men assembling a grill are preparing for a grilling competition.
This justifies what answer for what question? Q & A: 
Given the sentence "Two men are outside while assembling a grill." is it true that "There are men preparing for a grilling competition."?
it is not possible to tell
Not all men assembling a grill are preparing for a grilling competition.
This justifies what answer for what question? Q & A: 
user
Given the sentence "Two men are outside while assembling a grill." is it true that "There are men preparing for a grilling competition."?
it is not possible to tell
assistant
Not all men assembling a grill are preparing for a grilling competition.
This justifies what answer for what question? Q & A: 
Given the sentence "Two men are outside while assembling a grill." is it true that "There are men preparing for a grilling competition."?
it is not possible to tell