a boy looks into his telescope in a grassy field .
A boy is outside
a boy looks into his telescope in a grassy field.
A boy is outside
Based on the information that a boy is doing something in a grassy field, it can be inferred that the boy is outside.  Grassy fields are found outside.
Based on the information that a boy is doing something in a grassy field , it can be inferred that the boy is outside . Grassy fields are found outside .