One of the most important questions they had to consider was( ) of public healthA. what B. this C. that D. which

Some young soldiers who had recently joined the army were being trained in modern ways of fighting,and one of the things they were shown was how an unarmed man could trick an armed enemy and take his weapon away from him．First one of their two instructors took a knife away from the other,using only his bare hands;and then he took a rifle away from him in the same way．After the lesson,and before they went on to train the young soldiers to do these things themselves,the two instructors asked them a number of questions to see how well they had understood what they had been shown．One of the questions was this:“Well,you now know what an unarmed man can do against a man with a rifle．Imagine that you are guarding a bridge at night,and that you have a rifle．Suddenly you see an unarmed enemy soldier coming towards you．What will you do?”
The young soldier who had to answer this question thought carefully for a few seconds before he answered,and then said,“Well,after what I have just seen,I think that the first thing I would do would be to get rid of my rifle as quickly as I could,so that the unarmed enemy couldn't take it from me and kill me with it!”

The young soldier told the instructor that__．

A.the important thing was to be brave
B.the important thing was to save your life
C.the important thing was to have a gun
D.the important thing was to know the trick

When researchers first discovered a link in the late 1990s between childhood adversity and chronic health problem later in life, the real revelation was how common those experiences were across all socioeconomic groups. But the first major study to focus on adverse childhood experiences (ACEs) was limited to a single healthcare system in San Diego. A study published in JAMA Pediatrics- the largest nationally representative study to date on ACEs一confirms that these experiences are universal, yet highlights some disparities among socioeconomic groups.
The current study finds three out of five adults across the U.S. had at least one adverse experience in their childhood, such as divorce, a parent's death, physical or emotional abuse, or a family member's incarceration or substance abuse problem. A quarter of adults have at least three such experiences in childhood, which according to other research- increase their risk for most common chronic diseases, from heart disease and cancer to depression and substance abuse.
"This is the first study of this kind that alows us to talk about adverse childhood experience as a public health problem in the same way we talk about obesity or hypertension or any other highly prevalent population risk factor" says Adam Schickedanz, an assistant professor of pediatrics at the David Geffen School of Medicine at UCLA, who was not involved in the research. "Up until now,we haven't really had a study that takes a national look .
The study researchers, led by Centers for Disease Control and Prevention researcher Melissa T. Merrick, analyzed data from 214, 157 adults in 23 states recently. The participants answered 11 questions about whether they'd experienced what have now become well recognized as ACEs: parental separation or divorce, child abuse (physical, emotional and sexual ), domestic violence and living with someone who has been incarcerated or has a mental ilness or a substance use disorder.Nearly 62 percent of respondents had at least one ACE and a quarter reported three or more. The remaining respondents had at least two ACES, including 16 percent with four or more such experiences .Those identifying as black or Latino and those with less than a high school education or an annual income below $15,000 were more likely to have more ACES. Women, younger adults,unemployed people and those unable to work also tended to have more ACES. But Schickedant cautions that, while the disparities are real, it's important to recognize how common these experiences are among all people, including white and middle class families.”This study shows that ACEs affect people from all walks of life everywhere," he says.
This new study suggests that a need to target prevention resources where they can help most,says Jack Shonkoff, a professor of child health and development at the Harvard T. H. Chan School of Public Health. This requires identifying what makes some people more susceptible than others to the effects of adversity,“Nobody is immune to adverse experiences in childhood but for some population groups, they're a larger burden of childhood adversity than others." he says.
What can we learn from the passage?

A. There are gender differences in the effect of ACEs.
B. Genetics play an important role in health outcomes.
C. Middle class families are more likely to have more ACEs.
D. ACEs can exert lifelong impact on people's mental health.