______(49)A.To avoid being exploited mothers with

______(49)

A.To avoid being exploited,mothers with a partner hold back from working too hard if the father is being lazy,and it’s the chicks that pay the price.

B.To find out,they measured how much effort zebra finch parents put into raising their babies.

C.Those males reared by single mums were chosen more often than those from two一parent families.

D.With two parents around,there’s always a conflict of interests,which can have a detrimental effect on the quality of the offspring.

E.Kilner says conflict of parents should now be taken into account as well.

F.It turned out that single mums had greater influence on their offspring.