pay attention to the "than to", and you just realize, this sentence is simply comparing which one(sorghum and most other corn) is more related to the some corn.

It's like, the relationship between some corn and sorghum is stronger than some corn with most corn. so the A and B are Sorghum and Most Corn. the Quality they comparing is the retionship between them to Some corn..

The sentence just told us that "some people did a test" , it just a statement

this is may be a trap the testmaker set for tester. but it always help to realize some word hint could represents what type of claim

true