In the following question, four alternatives are given for the idiom/phrase in bold and italics in the sentence. Choose the alternative which best expresses the meaning of idiom/phrase.
Despite the trust bestowed on the minister he turned out to be a snake in the grass during the revolution.
a secret enemy
a treacherous person
an unforeseen danger
an unexpected misfortune
Correct answer is A
No explanation has been provided for this answer.