The correct answer is - B) 650.
The Red Sea is a sea that grows in size because it is widening all the time. The rate of the widening is 1.25 centimeters per year, so it is not something that can be easily seen during a normal human lifespan, but over a longer period of time it will have a much different shape, size, and influence in the region. It is located between the African and the Arabian tectonic plates as an elongated thin sea with a northwest-southeast direction.
The widening of the Red Sea is due to the movement of the tectonic plates. Africa is moving towards northwest, and that makes it slowly distance itself from the Arabian plate, thus opening more space for the Red Sea.
In order for the Red Sea to widen another 812.5 centimeters, will be required 650 years, and we can come to the result by simple dividing the required number of the width with the annual widening.
812.5 / 1.25 = 650.