What is the recommended weight gain and rate of gain for a twin pregnancy?
a) 37-54 lbs; 1.5 lbs/week
b) 31-50 lbs; 1.0-1.5 lbs/week
c) 25-42 lbs; 0.8-1.2 lbs/week
d) 20-35 lbs; 0.5-0.9 lbs/week