Test 2 Section 5 - #6 (page 464)

The key here is recognizing that slope = rise/run (or, in this question, y/x).  According to this question the slope of that ramp is 7/16.  We can actually BACKSOLVE this one, by basically taking our answers and plugging them into rise/run (or, like we said, y/x) to see which one will give us that same fraction.  We know our rise (or y) is 3.5 feet.  With backsolve, always try (C) first:

(C) 3.5/20 = 7/40.  Nope.  Way too long on bottom.  Go smaller.
(B) 3.5/12.5 = 7/25.  Still too long on bottom, but getting warmer...
(A) 3.5/8 = 7/16.  BINGO.