Children living at high altitudes develop a larger chest cavity by adulthood than children living at lower altitudes. this is an example of

Children's who live at high altitudes develop a larger chest cavity by adulthood than children who live at lower altitudes. It is an example of developmental adaptations which occurs at the level of the individual during the time of critical life stages.

Mediastinal tumors occur in the chest cavity and it contains the heart, trachea, connective tissue, thymus gland, and large blood vessels which are between the lungs. Chest mass in children and in infants may be secondary tumors.

Then it is june the conclusion to the second sentence is just restating "if it is june then it is summer"