Step 1: Order of adjectives rule.
When two or more adjectives are used, they should follow a general order: Opinion/quality → size → age → shape → color → origin → material → purpose.
Here: “black” (color) and “heavy” (quality/weight). Step 2: Correct order.
“heavy black steel trunk” — quality/weight before color.
\[
\boxed{\text{(B) Error in adjective order}}
\]