Answer:
huh what you mean by
Is that a question or telling a reason to someone.
I'm extremely sorry
I can't understand your question
Pls post it in proper way
You have to give us some more information...
A. Wasn't.. This is because if you seperatevthe contractioninto two words it is was not, this would make the sentence be "Wally was not capable of lifting the heavy box."
If you were to do the same thing with weren't it would sound like "wally were not capable of lifting the heavy box." This does not make sense because "wally" is singular (so is "was not") and "were not" is pleural.
Hope this helps