Please answer the following question: What is the name of the person whose only remaining son died in 840?  Answer the above question based on the context below:  Charlemagne planned to continue the Frankish tradition of dividing his kingdom between all his heirs, but was unable to do so as only one son, Louis the Pious (r. 814–840), was still alive by 813. Just before Charlemagne died in 814, he crowned Louis as his successor. Louis's reign of 26 years was marked by numerous divisions of the empire among his sons and, after 829, civil wars between various alliances of father and sons over the control of various parts of the empire. Eventually, Louis recognised his eldest son Lothair I (d. 855) as emperor and gave him Italy. Louis divided the rest of the empire between Lothair and Charles the Bald (d. 877), his youngest son. Lothair took East Francia, comprising both banks of the Rhine and eastwards, leaving Charles West Francia with the empire to the west of the Rhineland and the Alps. Louis the German (d. 876), the middle child, who had been rebellious to the last, was allowed to keep Bavaria under the suzerainty of his elder brother. The division was disputed. Pepin II of Aquitaine (d. after 864), the emperor's grandson, rebelled in a contest for Aquitaine, while Louis the German tried to annex all of East Francia. Louis the Pious died in 840, with the empire still in chaos.A three-year civil war followed his death. By the Treaty of Verdun (843), a kingdom between the Rhine and Rhone rivers was created for Lothair to go with his lands in Italy, and his imperial title was recognised. Louis the German was in control of Bavaria and the eastern lands in modern-day Germany. Charles the Bald received the western Frankish lands, comprising most of modern-day France. Charlemagne's grandsons and great-grandsons divided their kingdoms between their descendants, eventually causing all internal cohesion to be lost. In 987 the Carolingian dynasty was replaced in the western lands, with the crowning of Hugh Capet (r. 987–996) as king. In the eastern lands the dynasty had died out earlier, in 911, with the death of Louis the Child, and the selection of the unrelated Conrad I (r....
A:
Charlemagne