Step 1: Understanding the Question:
This question tests knowledge of 2,4-D and its functions.
Step 2: Detailed Explanation:
2,4-D is a synthetic auxin, which makes it a growth regulator (A).
It is also widely used as a herbicide (D) for controlling broadleaf weeds.
It is not a mutagen (B) or a gaseous hormone (C).
Ethylene is a gaseous hormone.
Thus, 2,4-D is both a growth regulator and a herbicide.
Step 3: Final Answer:
Thus, 2,4-D is a growth regulator and a herbicide, which corresponds to option (D).
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