Question: Who is Empress Wang (Gaozong)'s mother-in-law?

Knowledge 1: Empress Wang (Gaozong)
Empress Wang (628 – 27 November 655) was an empress of the Chinese dynasty Tang Dynasty.She was the first wife and empress of Emperor Gaozong and became empress shortly after he became emperor in 649.She, however, did not bear any sons for him and was not favored.Therefore, in apprehension that one of his concubines, Consort Xiao, who was both favored and had a son, might seek to displace her, she recommended a former concubine of Emperor Gaozong's father Emperor Taizong, Consort Wu (later known as Wu Zetian), to be Emperor Gaozong's concubine as well, hoping to divert favor from Consort Xiao.Soon, however, Consort Wu became dominant in the palace and overwhelmed both Empress Wang and Consort Xiao, eventually accusing them of using witchcraft against Emperor Gaozong.Emperor Gaozong reduced both Empress Wang and Consort Xiao to commoner rank and put them under arrest in 655, replacing Empress Wang with Consort Wu.Soon, Empress Wang and Consort Xiao were executed on the new Empress Wu's orders. [SEP] Knowledge 2: Emperor Gaozong of Tang
Emperor Gaozong of Tang (21 July 628 – 27 December 683), personal name Li Zhi, was the third emperor of the Tang dynasty in China, ruling from 649 to 683 (although after January 665 power and governance was primarily in the hands of his powerful second wife Empress Wu, later known as Wu Zetian).Emperor Gaozong was the son of Emperor Taizong and Empress Zhangsun.Emperor Gaozong was aided in his rule by Empress Wu during the later years of his reign after a series of strokes left him incapacitated.Emperor Gaozong delegated all matters of state to his Strong wife and after he died in 683, power fell completely into the hands of Empress Wu, who subsequently became the only Empress regnant in Chinese history.After his death, he was interred at the Qianling Mausoleum along with Wu Zetian.Historians have generally viewed Emperor Gaozong as a weak ruler, inattentive to the business of the state and leaving such business to his powerful wife Empress Wu.During the first part of his reign, Tang territorial gains, which started with his father Emperor Taizong, continued, including the conquest of Baekje, Goguryeo, and the Western Turkic Khaganate, but throughout the 670s, much of those gains were lost to the Tibetan Empire, Silla, Khitan, and Balhae.Further, territory previously conquered that belonged to both the Göktürks and the Western Turkic Khaganate were subjected to repeated rebellions.
Knowledge 1: Emperor Gaozong of Tang
Emperor Gaozong of Tang (21 July 628 – 27 December 683), personal name Li Zhi, was the third emperor of the Tang dynasty in China, ruling from 649 to 683 (although after January 665 power and governance was primarily in the hands of his powerful second wife Empress Wu, later known as Wu Zetian).Emperor Gaozong was the son of Emperor Taizong and Empress Zhangsun.Emperor Gaozong was aided in his rule by Empress Wu during the later years of his reign after a series of strokes left him incapacitated.Emperor Gaozong delegated all matters of state to his Strong wife and after he died in 683, power fell completely into the hands of Empress Wu, who subsequently became the only Empress regnant in Chinese history.After his death, he was interred at the Qianling Mausoleum along with Wu Zetian.Historians have generally viewed Emperor Gaozong as a weak ruler, inattentive to the business of the state and leaving such business to his powerful wife Empress Wu.During the first part of his reign, Tang territorial gains, which started with his father Emperor Taizong, continued, including the conquest of Baekje, Goguryeo, and the Western Turkic Khaganate, but throughout the 670s, much of those gains were lost to the Tibetan Empire, Silla, Khitan, and Balhae.Further, territory previously conquered that belonged to both the Göktürks and the Western Turkic Khaganate were subjected to repeated rebellions. [SEP] Knowledge 2: Empress Wang (Chenghua)
Empress Wang, formally Empress Xiaozhenchun (died 1518) was a Chinese Empress consort of the Ming Dynasty, married to the Chenghua Emperor.Empress Wang was chosen by the emperor to the position of empress after her predecessor had been deposed due to a conflict with the emperors favorite concubine, Consort Wan.Aware of the mistake of her predecessor, Wang was very anxious to avoid any conflict with the emperors favorite.Consort Wan had no son with the emperor after her first son died in infancy, and feared the competition if any other of the emperors consorts or concubines gave birth to a son.It was said that empress Wang deliberately stayed childless to avoid such a conflict with Consort Wan.The efforts to avoid all conflicts with Consort Wan and to show herself submissive to her, did secure the position of empress Wang at court.In 1487, the Chenghua Emperor died, and empress Wang was given the title Empress Dowager.The Hongzhi Emperor granted her the title Grand Empress Dowager.In 1510, she was further raised in rank by the then-reigning emperor, Emperor Zhengde, who was the eldest son of the Hongzhi Emperor and the grandson of the Chenghua Emperor.
Knowledge 1: Empress Wang (Gaozong)
Empress Wang (628 – 27 November 655) was an empress of the Chinese dynasty Tang Dynasty.She was the first wife and empress of Emperor Gaozong and became empress shortly after he became emperor in 649.She, however, did not bear any sons for him and was not favored.Therefore, in apprehension that one of his concubines, Consort Xiao, who was both favored and had a son, might seek to displace her, she recommended a former concubine of Emperor Gaozong's father Emperor Taizong, Consort Wu (later known as Wu Zetian), to be Emperor Gaozong's concubine as well, hoping to divert favor from Consort Xiao.Soon, however, Consort Wu became dominant in the palace and overwhelmed both Empress Wang and Consort Xiao, eventually accusing them of using witchcraft against Emperor Gaozong.Emperor Gaozong reduced both Empress Wang and Consort Xiao to commoner rank and put them under arrest in 655, replacing Empress Wang with Consort Wu.Soon, Empress Wang and Consort Xiao were executed on the new Empress Wu's orders. [SEP] Knowledge 2: Empress Wang (Chenghua)
Empress Wang, formally Empress Xiaozhenchun (died 1518) was a Chinese Empress consort of the Ming Dynasty, married to the Chenghua Emperor.Empress Wang was chosen by the emperor to the position of empress after her predecessor had been deposed due to a conflict with the emperors favorite concubine, Consort Wan.Aware of the mistake of her predecessor, Wang was very anxious to avoid any conflict with the emperors favorite.Consort Wan had no son with the emperor after her first son died in infancy, and feared the competition if any other of the emperors consorts or concubines gave birth to a son.It was said that empress Wang deliberately stayed childless to avoid such a conflict with Consort Wan.The efforts to avoid all conflicts with Consort Wan and to show herself submissive to her, did secure the position of empress Wang at court.In 1487, the Chenghua Emperor died, and empress Wang was given the title Empress Dowager.The Hongzhi Emperor granted her the title Grand Empress Dowager.In 1510, she was further raised in rank by the then-reigning emperor, Emperor Zhengde, who was the eldest son of the Hongzhi Emperor and the grandson of the Chenghua Emperor.

Answer: Empress Zhangsun