In what trimester does these happen

a sac called a placenta forms around the embryo and is connected to the embryo with an umbilical cord.
a) first
b) second
c) third

Emma recently found out she was pregnant. every thursday evening for the next six weeks, emma and her mother will attend a special program that prepares pregnant teens to become mothers. during the first class, emma learned about the stages of childbirth. what was the order she was taught? first, emma learned about  .then, she learned about the    stage. next, emma learned about  .last, she learned about the    stage