<p>surface mining is safer, quicker, and cheaper than depp mining, but <em>the greater is its toll in human misery</em>.</p>
<p>a. the greater is its toll in human misery
b. it has a greater human misery toll
c. in its human misery toll it is greater
d. there is the greater toll in human misery
e. its toll in human misery is great</p>
<p>the answer is obvious but i'm unsure of why (according to cb's explanations) "it" is ambiguous but "its" is not.</p>