Was certain about (4)
I believe the answer is:
knew
(Other definitions for knew that I've seen before include "Was conscious of" , "Recognised" , "Was aware of the fact" , "Was familiar with" , "Was cognizant of" .)
I believe the answer is:
knew
(Other definitions for knew that I've seen before include "Was conscious of" , "Recognised" , "Was aware of the fact" , "Was familiar with" , "Was cognizant of" .)