1
Somsak carried out an activity to test the hardness of some objects. He wanted to determine which object is harder. He used object X to scratch some objects. The results are shown in the table below.
| Object being scratched | Any scratch marks left on the object |
| Wooden plank | Yes |
| Plastic ruler | Yes |
| Eraser | Yes |
| Steel ruler | No |
Which of the following is correct?
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- Object X is harder than the wooden plank and plastic ruler only.
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- The steel ruler is harder than object X.
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- The wooden plank, plastic ruler and eraser are harder than object X.
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- Object X is the hardest among the objects.