We scrambled backwards , but then there was another explosion behind us . BAM . We heard laughter , and when we looked up , we saw some kids on the roof , and they were hurtling cement construction blocks off the roof and down on our heads , and it was these concrete blocks that were shattering on the sidewalk around us . We took off running , yelling back at these maniacal attackers .

Question: What 's a possible reason the kids were hurtling cement construction blocks off the roof and down on people 's heads ?
Answer: Because they are stupid and are n't thinking about the potential consequences .None of the above choices .Because there was another explosion behind the writer .Because they heard laughter .