"Tie the knot" in the first line of the first paragraph means ______.

A．Living together before marriage is now more acceptable than before.
B．Little household chores can cause trouble in one's marriage.
C．love is the guarantee of a happy marriage.
D．Newly-weds often has many life imbalances to face.

A．it is immoral and inappropriate
B．it may end a relationship more quickly
C．it is a shame to the couple's parents
D．it will cause many social problems