This is why B is right. I initially had doubts about the replacing seeds thing, thinking that if we're replacing a diseased plant with another of the same strain, that new plant is just going to get the disease. By that logic, B is useless. HOWEVER, B is insinuating that there are different strains in the bank than what is planted. So if we have strains A, B, and C planted, and C becomes diseased, it is not disaster because we have strains X, Y, and Z in the bank to replace C with.

I hope this helps explain why B is correct!

I made this mistake as well, and at first I was only more confused after the answer explanation. Here is what made it click for me:

The answer choice specifies Planck's contributions to CLASSICAL wave theory. The contributions we see detailed in the passage are his contributions to overthrowing an assumption of classical wave theory.

Essentially, Planck made contributions that were pro-classical, but we don't know what those are. The contribution in the next sentence is anti-classical.

Hope that helps! Looking at it like that made it make more sense for me.

thank you for this!! I completely agree with you that the difference between all of the descriptors is so marginally small that it doesn't make sense to nitpick that issue. Never vs Not always makes so much more sense to me there

I did the same thing! So frustrating, I was on fire lol