'The struggle this time is a struggle --- emancipation."

The correct answer for the given question, "The struggle this time is a struggle --- emancipation," is "for." We use the preposition "for" in this context to indicate the desired outcome or purpose of the struggle. In simpler terms, the word "for" shows that the struggle is not happening just because of emancipation or against emancipation, but rather it is a struggle that is aimed towards achieving emancipation. It implies that the struggle is being fought in support of, or in order to bring about, emancipation.