Which of the following statements is/are correct?
I. Polythene is a thermosetting plastic.
II. All plastics can be easily softened on heating III. Plastics are non reactive towards air and water.
IV. Plastics are good conductors of heat and electricity.

Options

A. I and II only
B. III only
C. III and IV only
D. I, II, III and IV

Explanation

To determine which statements are correct regarding plastics, let's analyze each statement one by one.

### Step 1: Analyze Statement I
**Statement I:** Polythene is a thermosetting plastic.
**Analysis:** This statement is incorrect. Polythene (polyethylene) is a thermoplastic, not a thermosetting plastic. Thermoplastics can be re-molded and softened upon heating, while thermosetting plastics cannot.
**Conclusion:** **False**

### Step 2: Analyze Statement II
**Statement II:** All plastics can be easily softened on heating.
**Analysis:** This statement is also incorrect. Only thermoplastics can be softened upon heating. Thermosetting plastics, once set, cannot be softened or re-molded.
**Conclusion:** **False**

### Step 3: Analyze Statement III
**Statement III:** Plastics are non-reactive towards air and water.
**Analysis:** This statement is generally true. Most plastics are resistant to air and water, making them non-reactive in these conditions. However, some plastics can degrade under certain conditions, but as a general rule, they are considered non-reactive.
**Conclusion:** **True**

### Step 4: Analyze Statement IV
**Statement IV:** Plastics are good conductors of heat and electricity.
**Analysis:** This statement is incorrect. Plastics are generally poor conductors of heat and electricity; they are considered insulators.
**Conclusion:** **False**

### Final Conclusion
Based on the analysis:
- Statement I: False
- Statement II: False
- Statement III: True
- Statement IV: False

Thus, the only correct statement is **III**.

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