Intelligence test scores follow an approximately normal distribution, (meaning) that most people score near the middle of the distribution of scores, (and) scores (drop off) fairly rapidly in frequency as one moves in (either) direction from tile center.

A．accepted
B．what
C．there is
D．one of

Most of the changes (occurred) in pattens of family planning (had taken place) before public family services were established and at (considerable) emotional and physical costs (to many couples).