Answer:
12 hours to 24 hours
Step-by-step explanation:
The correct answer that fills up the given blank most appropriately is " 12 hours to 24 hours " of leaving the ovary.
This is because of the fact that the egg remains in the fallopian tube after it is being released for about 24 hours. Thus, for the effective conception to take place, the egg must fuse with the sperm within this duration.