Question

they have finally....it,for years scientists debated whether the sound of crackling knuckles came​

Answer 1

Explanation:

they have finally done it,for years scientists debated whether the sound of crackling knuckles came

Answer 2

Explanation:

they have finally....it,for years scientists debated whether the sound of crackling knuckles

they have finally. done .it,for years scientists debated whether the sound of crackling knuckles

the missing word is done as it is in present perfect tense ..