Synonym of GRAVE

Answer: Option D

Formidable : inspiring fear or respect through being impressively large, powerful, intense, or capable.
Bitter : having a sharp, pungent taste or smell; not sweet.
Pregnant : (of a woman or female animal) having a child or young developing in the uterus.
Solemn : not cheerful or smiling; serious.
Grave : serious or solemn in manner or appearance.

Synonym of Grave is Solemn