BOZEMAN, Mont. (AP) — Authorities say four people, including three children, were hospitalized after a gas explosion at a home in West Yellowstone. Shane Grube, chief of the Hebgen Basin Rural Fire District said firefighters were called to the mobile home Tuesday morning. He says the explosion caused a fireball that blew itself out. Two people suffered severe injuries and two were moderately injured. All of the victims were taken to a hospital in Rexburg, Idaho. The fire district is investigating with help from the state fire marshal’s office. No other details were released.
One adult was injured in the explosion.
This is correct because the text says that four people were hospitalized, and three of them were children.  Therefore we can assume the fourth was an adult.  This is tricky because it needs to be inferred from the text.
( z1 injure :ARG0 ( z2 explode ) :ARG1 ( z3 adult :quant 1 ) )