According to a U.S. survey, one third of all school aged children in the United States are, for some part of the week, latch key kids; that is, they go home to an empty house. The total number may be between five and seven million children between 5 and 13 years old. The survey found that 15% were home alone before school, 76% after school and 9% at night. Perhaps, the 9% have parents who work at night.
One-half of all children in the country aged 12 to 14 are home alone an average of seven hours a week. The very poor in America are less likely(可能) to leave their children alone at home, or allow them to go home alone, than families who earn much more. This is probably because the very poor live in less safe neighborhoods, and have fewer friends or family who can help in case of emergency(在紧急情况下). Though they work for hours, working mothers spend an average of five-and-a-half hours a day with their children.
Among these latch key children, we know that about 51% are doing poorly in school. Most teachers believe that being alone at home is the number one cause of school failure. Home-alone children are more likely to become unhappy, smoke cigarettes and drink wine. They are also more likely to abuse drugs（吸毒）.
1. According to the U.S. survey, ___________ are latch key kids.
A. two thirds of all school age children
B. about 33.3% of all school age children
C. five million
D. seven million
2. ___________ in America are more likely to leave their children alone at home.
A. The very poor B. The families in the countryside
C. The families in the city D. The families who earn much more
3. Latch key kids don’t mean that ______________.
A. kids go home to an empty house
B. they are more likely to become unhappy, smoke cigarettes and drink alcohol
C. they are more likely to do well in school
D. they are more likely to abuse drugs
4. The passage mainly tells us __________.
A. some things about the latch key kids in America
B. one-half of all children in the country aged 8 to 10 are home alone
C. being alone at home causes all school failure
D. 9% of the latch key kids’ parents work at night