题干

将烧瓶内的水加热至沸腾后移去火焰,水会停止沸腾,迅速塞上瓶塞,把烧瓶倒置并向瓶底浇冷水.如图所示,你会观察到烧瓶内的水会再次沸腾起来.则下列说法正确的是(   )

A:移去火焰,水停止沸腾是因为瓶内水的沸点升高了

B:浇冷水,水能再次沸腾是因为瓶内的气压降低了

C:浇冷水,水能再次沸腾是因为瓶内水的温度升高了

D:这两次水的沸点相同

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答案(点此获取答案解析)

B

同类题5

阅读理解

    Childhood is a happy time, right? Not necessarily. Consider these facts.

Depression(抑郁症) may occur in as many as 1 in 33 children.

    Once a child has an episode of depression, he or she has a 50 percent chance of experiencing another episode in the next 5 years.

    Suicide(自杀) is the 6th leading cause of death for 5-to-15-year-olds.

    If your child experiences 5 or more of these signs or symptoms for at least 2 weeks, he or she may be experiencing depression or mental illness.

Feeling--Does your child demonstrate:

Sadness          Emptiness

Hopelessness      Guilt

Worthlessness

Lack of enjoyment in everyday pleasures

Thinking--Is your child having trouble:

Concentrating

Making decisions

Completing schoolwork

Maintaining grades

Maintaining friendships

Physical problems--Does your child complain of

Headaches        Stomachaches

Lack of energy

Sleeping problems ( too much or too little)

Weight or appetite changes ( gain or loss)

Suicide risk--Does your child talk or think about:

Suicide

Death

Other morbid(生病的)

subjects

Behavior problems--Is your child:

Irritable          Not wanting to go to school

Wanting to be alone most of the time

Having difficulty getting along with others

Cutting classes or skipping school

Dropping out of sports, hobbies or other activities

Drinking alcohol or using drugs

    Sometimes, a child who causes problems at school or at home may actually be depressed, according to the American Academy of Child and Adolescent Psychiatry.

    If you think your child may be depressed, it's important to have your child treated. Discuss your child's problems with his or her doctor. The doctor may suggest a referral to a children's psychologist or psychiatrist.