American doctors say that mothers who smoke cigarettes before their babies are born may slow the growth of their babies' lungs. They say reduced lung growth could cause the babies to suffer breathing problems and lung diseases later in life. Doctors in Boston, Massachusetts studied 1,000 children. The mothers of some of the children smoked, while the other mothers did not. Doctors found that the lungs of the children whose mothers smoked were 8% less developed than the lungs of the children whose mothers did not smoke, and that the children whose mothers smoked had 25% more cold and breathing diseases than other children later in life. Another recent study found that children had a greater chance of having lung cancer if their mothers smoked. The study also showed that the danger of cancer increased only for sons and not for daughters, and that the father's smoking did not affect a child's chance of suffering from lung cancer. According to the passage, the writer wants to tell us   _  .
The danger of cancer increased only for girls and not for sons The children whose mothers smoked had a quarter more cold and breathing diseases than other children later in life The father's smoking influenced a child's chance of suffering from lung cancer The lungs of the children whose mothers smoked were 8% more developed than those of the children whose mothers did not smoke
Question: American doctors say that mothers who smoke cigarettes before their babies are born may slow the growth of their babies' lungs. They say reduced lung growth could cause the babies to suffer breathing problems and lung diseases later in life. Doctors in Boston, Massachusetts studied 1,000 children. The mothers of some of the children smoked, while the other mothers did not. Doctors found that the lungs of the children whose mothers smoked were 8% less developed than the lungs of the children whose mothers did not smoke, and that the children whose mothers smoked had 25% more cold and breathing diseases than other children later in life. Another recent study found that children had a greater chance of having lung cancer if their mothers smoked. The study also showed that the danger of cancer increased only for sons and not for daughters, and that the father's smoking did not affect a child's chance of suffering from lung cancer. According to the passage, the writer wants to tell us   _  .
A. The danger of cancer increased only for girls and not for sons
B. The children whose mothers smoked had a quarter more cold and breathing diseases than other children later in life
C. The father's smoking influenced a child's chance of suffering from lung cancer
D. The lungs of the children whose mothers smoked were 8% more developed than those of the children whose mothers did not smoke
Answer: