Big Book- Test 12- Text Completion

Good morning, Could someone please help me understand the reasoning of the question below:

(Section 6)
Q- The chances that a species will _______ are reduced if any vital function is restricted to a single kind of organ; ________ by itself possess an enormous survival disadvantage.

A- I could figure out the answer to the first blank, which is persist but the answer to the second blank is redundancy, which I am not able to fathom.

Thanks in advance!

Can you post the answer choices.
You can do process of elimination to get the answer

Thanks for your time!

These were the answer choices:-

a) degenerate…complexity
b) expire… size
c) disappear… variety
d) flourish… symmetry
e) persist… redundancy

From the first blank, options A B and C can be eliminated.
For the 2nd blank, notice that the first part of the sentence says that chances of survival are reduced if only one kind of organ is given the most important tasks. Hence, only redundant works, as it means that even if one organ fails, another can do its job.

Alright! Thanks a ton @zetakill