1. 

INEXPLICABLE
A. Confusing
B. Unaccountable
C. Chaotic
D. Unconnected

Answer: Option B

Explanation:

Inexplicable : mean unable to explain to anyone. That is what unaccountable.

Synonyms: baffling, enigmatic, incomprehensible, indecipherable, indescribable, inexplainable, inscrutable, insoluble, mysterious, mystifying, obscure, odd, peculiar, puzzling, strange, unaccountable, undefinable, unexplainable, unfathomable, unintelligible, unsolvable.