When _______ figure out the gravity, Newton was lying under an apple tree.A.he triesB.tryingC.try toD.trying to

To fill in the blank in the sentence, we need to analyze the context of the sentence and how the options fit grammatically.

Analysis of Options

1. A. he tries - This is in the present tense, which does not fit because the sentence refers to a past event.
2. B. trying - This form, as a gerund or participle, does not fit well because it requires a more complete structure.
3. C. try to - This suggests an intention or attempt but does not agree with the structure of the sentence.
4. D. trying to - This option creates a participial clause that fits well with the context, indicating that while Newton was trying to figure out gravity, he was also lying under the apple tree.

Conclusion

The correct answer is D. trying to.

Final Answer

D. trying to