这种食品添加剂的味道尝起来很不自然。

The flavor of this food additive tastes ___unnatural.

她对自己孩子的冷漠态度看起来很不自然。

Her indifferent attitude towards her own child seemed ___unnatural.

他的笑容看起来很勉强，一点都不自然。

His smile looked ___unnatural and forced.