Complex sentence: The US Air Force studied various improvements to the AGM-158, resulting in the development of the JASSM-Extended Range (JASSM-ER), which received the designation AGM-158B in 2002.
Split into simpler sentences: The US Air Force is studying various improvements to the AGM-158. The JASSM-Extended Range (JASSM-ER) received the designation AGM-158B in 2002.