Which of the following pairs of rocks is not correctly shown?

Analyze the question: The pairs show a parent rock changing into a metamorphic rock through heat and pressure. We need the pair that is not correct.

Concept: Metamorphism changes existing rocks into new ones without melting them. Common examples:

| Original rock | Metamorphic rock | |---|---| | Clay / shale / mudstone | Slate (then phyllite, schist) | | Limestone | Marble | | Sandstone | Quartzite | | Coal | Anthracite, then graphite | | Granite | Gneiss |

Checking each option:

• A. clay → slate: Correct. Clay and shale are metamorphosed into slate.
• B. limestone → marble: Correct. Heat and pressure recrystallize limestone into marble.
• C. sandstone → quartzite: Correct. The sand grains fuse into very hard quartzite.
• D. shale → graphite: Not correct. Shale becomes slate. Graphite comes from carbon-rich material such as coal, which goes through anthracite and then graphite.

Tip: Memorize the pairs as "Shale → Slate, Limestone → Marble, Sandstone → Quartzite, Coal → Graphite/Anthracite, Granite → Gneiss." Notice that the first letters often match (Shale-Slate, Sandstone-Quartzite is the exception). If a pair breaks the pattern, check it carefully.