The correct option is B -,
The double dash -- contains two em dashes, which are longer in length
than the hyphen. Depending on the context, they can replace the
parentheses, comma and colon. It's more informal, compared to the
parentheses. It adds emphasis to a group of words that it encloses,
hence separating it from the sentence. When the double dash is used to enclose additional information, the surrounding punctuation shall be omitted, hence the comma, which previously followed the parentheses shall be omitted. Since the comma has not been omitted, it is the error here and we have to choose option C. Exclamation marks '!' indicate surprise or a command that requires immediate action, here the phrase requires quick action, hence it's not an error and we do not choose option A. The double dash -- has replaced parenthesis, it encloses additional information, at the same time, brings emphasis to it. hence it's not an error and we don't have to choose option B. Full stops '.' are used at the end of a sentence like in the given one, hence it's not an error and we don't have to choose option D.