OK, so the sentence is in the form of: "Caribou are wary animals with excellent hearing, so [some kind of action] required exceptional hunting skill."
but they just made it more complicated by adding a lot of "fluff":"Caribou are wary animals with excellent hearing,
so stalking them over the treeless landscape, getting close enough to kill it with nothing but a handheld lance, as Dorset people did, required exceptional hunting skill."
Well, there's some discrepancy here:
"stalking THEM"
"getting close enough to kill IT"
THEM is not consistent with IT. Something sounds weird.You seem to have gotten this far as you chose answer (C), which correctly replaces IT with ONE.However, the problem with (C), is that it leaves something hanging.
Answer (C) does not make sense: "so in order to stalk them...blah blah blah...required exceptional hunting skill."
Answer (C) would make sense if it were more like this:"so in order to stalk them....blah blah blah...the hunter had to have exceptional hunting skill."But since the latter part of the sentence ("required exceptional hunting skill") is
NOT underlined, then we must keep it as is and look for another answer choice.
Now with answer choice (B), we fix the original issue of replacing IT with ONE.
But it also makes sense..."to stalk them...blah blah blah...required exceptional hunting skill."
This makes sense! It's in the form of "To Do [X] required [Y]" --Answer (B) --notice you don't need to mention the subject in this case.
Notice how answer (C) would have had to look in order to be correct (must include the subject "hunter"): "In order to Do [X], a hunter required [Y]---
but since this is not what (C) is you have to go with answer (B)Hope that helps