Question:
Who was the chair of Yenching University in Apr, 1951?

Context:
 John Leighton Stuart is the chair of Yenching University from Jan, 1919 to Jan, 1945. 
 Lu Zhiwei is the chair of Yenching University from Jan, 1945 to Jan, 1949. 
 Weng Dujian is the chair of Yenching University from Jan, 1949 to Jan, 1952.

Answer:
Question:
Who was the chair of Yenching University in Apr, 1951?

Context:
 John Leighton Stuart is the chair of Yenching University from Jan, 1919 to Jan, 1945. 
 Lu Zhiwei is the chair of Yenching University from Jan, 1945 to Jan, 1949. 
 Weng Dujian is the chair of Yenching University from Jan, 1949 to Jan, 1952.

Answer:
user
Weng Dujian
assistant
Question:
Who was the chair of Yenching University in Apr, 1951?

Context:
 John Leighton Stuart is the chair of Yenching University from Jan, 1919 to Jan, 1945. 
 Lu Zhiwei is the chair of Yenching University from Jan, 1945 to Jan, 1949. 
 Weng Dujian is the chair of Yenching University from Jan, 1949 to Jan, 1952.

Answer:
user
Lu Zhiwei
John Leighton Stuart
assistant
Question:
Who was the chair of Yenching University in Apr, 1951?

Context:
 John Leighton Stuart is the chair of Yenching University from Jan, 1919 to Jan, 1945. 
 Lu Zhiwei is the chair of Yenching University from Jan, 1945 to Jan, 1949. 
 Weng Dujian is the chair of Yenching University from Jan, 1949 to Jan, 1952.

Answer:
user
Weng Dujian
assistant