根据材料回答下列各题： 第一篇Single-parent Kids Do Best Single mums are better at raising their kids than two parents—at least in the bird world. Mother zebra finches have to work harder and raise fewer chicks on their own, but they also produce more at-tractive sons who are more likely to get a mate. The finding shows that family conflict is as important an evolutionary driving force as. ecologicalfactors such as hunting and food supply. With two parents around, theres always a conflict of inter-ests, which can have a detrimental effect on the quality of the offspring. In evolutionary terms, the best strategy for any parent in the animal world is to find someone elseto care for their offspring, so they can concentrate on breeding again. So its normal for parents to tryto pass the buck to each other. But Ian Hartley from the University of Lancaster and his team won-dered how families solve this conflict, and how the conflict itself affects the offspring. To find out, they measured how much effort zebra finch parents put into raising their babies.They compared single females with pairs, by monitoring the amount of food each parent collected, andremoving or adding chicks so that each pair of birds was raising four chicks, and each single mum hadtwo—supposedly the same amount of work. But single mums, they found, put in about 25 per cent more~ effort, than females rearing with theirmate. To avoid being exploited, mothers with a partner hold back from working too hard if the fatheris being lazy, and it s the chicks that pay the price. "The offspring suffer some of the.cost of this con-flict" says Hartley. The cost does not show in any obvious decrease in size or weight, but in how attractive they are tothe opposite sex. When the chicks were mature, the researchers tested the "fitness" of the male off-spring by offering females their choice of partner. Those males reared by single mums were chosenmore often than those from two-parent families. Sexual conflict has long been thought to affect the quality of care given to offspring, says zoolo-gist Rebecca Kilner at Cambridge University, who works on conflict of parents in birds. "But the ex-perimental evidence is not great. The breakthrough here is showing it empirically." More surprising,says Kilner, is Hartleys statement that conflict may be a strong influence on the evolution of behav-ior, clutch size and even appearance. "People have not really made that link," says Hartley. A femalesreproductive strategy is usually thought to be affected by hunting and food supply. Kilner says conflictof parents should now be taken into account as well. With which of the following statements would the author probably agree？

A. Single mums produce stronger sons.
B. Single mums do not produce daughters.
C. Two-parent families produce less attractive children.
D. Two-parent families produce more beautiful offspring.