Final answer:
The correct sentence is: 'After the grill is fired up, let it get hot before you put on the chicken.'
Step-by-step explanation:
The correct sentence is: 'After the grill is fired up, let it get hot before you put on the chicken.' The verb form 'are putting' is incorrect because it is not the appropriate tense in this sentence. Instead, 'put' is the correct form to use. Other options like 'had put' and 'will put' are also unnecessary. The sentence is already in the present tense, so the simple present form 'put' is sufficient.
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