The technique of using words with the same vowel sound is A. alliteration. B. rhyme. C. assonance. D. simile.

C. Assonance, the repetition of the sound of a vowel in poetry.

Explanation:

the answer is subjective. i personally agree with the first answer for this question.

if one isn't strictly talking about objects then the correct answer would be 'my eyes' since according to this riddle i am asleep and in order to answer/open the door i need to open my eyes first of all.

however, if one is specifically looking for an object, then the first thing i would open would be the door

hope this !