The problem figure shows the top view of an object. Identify the correct elevation from amongst the answer figures looking in the direction of the arrow.
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The plan is divided by three vertical lines into four strips, so the profile has three internal ridge or valley points and four sloping faces.
The top view is a rectangle divided by three vertical lines into four strips of roughly 30%, 21%, 26% and 23% of the width. A line on the plan of a roof marks a ridge or a valley, so the roof has four sloping faces separated by three folds, at about 30%, 51% and 77% of the width. Seen from the front (the arrow points up the plan, so left stays left), the roof outline is a zig-zag with 4 slopes, and the elevation is a rectangle with this zig-zag top and plain vertical sides. Option (1) has only three slopes and a vertical step; option (3) has five slopes, with an extra fold inside the first strip; option (4) also has five slopes with a deep spike. Option (2) has exactly four slopes with folds near 28%, 47% and 78%, matching the plan. Answer: (2) the elevation with a four-slope zig-zag roof
