Step 1: Understanding the Question:
This question tests knowledge of the history of insecticide discovery.
Step 2: Detailed Explanation:
The insecticidal property of DDT was discovered by Paul Muller in 1939.
DDT was first synthesized in 1874, but its insecticidal properties were discovered later.
Muller won the Nobel Prize in 1948 for this discovery.
1932 (B), 1942 (D) are incorrect.
Thus, 1939 is the correct year.
Step 3: Final Answer:
Thus, DDT was discovered by Paul Muller in 1939, which corresponds to option (C).
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