"A" implies a singular subject, in this case it is the first boy. There are two more boys, plus another "one". By adding these, you get a total of 4 boys.


Context: "A young boy in a white shirt is chasing a soccer ball while two boys in blue shirts and one boy in an unidentified color shirt are chasing him." Claim: "There are 4 boys pictured."
Considering the context, is the claim true, false, or unknown?