which of the following geographical features acted as a natural defense for Egypt against enemies from the south?

I just took a test with the same question as this. I believe the answer that I put was C : cataracts of the Nile, or something like that. I got a 96% on the test (meaning I got one wrong, and I can't check to see which one I got wrong) but I'm 100% almost sure that I got this right.

Explanation:

If I remember correctly from my notes and the lecture, the cataracts of the Nile are very rapid and flow awfully fast, which is dangerous in most cases. Therefore, people wanting to invade Egypt from the south would have the get through these cataracts, which I'm pretty sure is not easy task.

If the comment section is available for access, please let me know if this is correct, I hope it is and that I helped you! :)

Have a good morning/afternoon/night! <3

arresting and exicuting citizens

the award is named for an american naval historian and theorist, rear admiral alfred thayer mahan, united states navy who, through his writing, provided stimulus and guidance to those who share in the defense of the nation.