Question:
Who was the head of state of Khmer Republic in Apr, 1975?

Context:
 Saukam Khoy is the head of the state of Khmer Republic from Apr, 1975 to Apr, 1975. 
 Lon Nol is the head of the state of Khmer Republic from Mar, 1972 to Apr, 1975. 
 Sak Sutsakhan is the head of the state of Khmer Republic from Apr, 1975 to Apr, 1975.

Answer:
Sak Sutsakhan