The clearest example of cause and effect is: D) If flooding where to go unchecked, steel support beams in buildings would rust.
Although everything happens for a reasin, in this sentence we can clearly see the cause and the effect. The cause is "if flooding where to go unchecked" and the effect is "steel support beams in buildings would rust". The first action makes the second happen. Rememner that in a cause effect relationship, one event makes another happen.
In option A we can't see the cause, we only have some information about Manhattan's future.
Option B also skips the cause, we don't know why the water has to be bumped.
Option C only compares two kinds of bridges.
