The food served at the official dinner was very bland.

Answer: Option D

Bland : (of food or drink) unseasoned, mild-tasting, or insipid.
Inedible : not fit or suitable for eating.
Spicy : flavoured with or fragrant with spice.
Nutritious : efficient as food; nourishing.
Tasty : (of food) having a pleasant, distinct flavour.

Antonym of Bland is Tasty