Respuesta :

coochicans
The best answer for the underlined word would be A: Vital

crucial means important or urgent.

required could be it but it does not imply a great amount of necessity.
The rest of the options don't even relate to this question.
KatieRowe
The answer is "A" Vital.

Example- If someone got there tooth knocked out, it would be vital to put it in milk.