给下图中的轴对称图形画出对称轴．

Talk quietly.

在平面直角坐标系中，正方形ABCD的顶点A、B、C的坐标分别为（-1，1）、（-1，-1）、（1，-1），则顶点D的坐标为____．

小阳通过图所示的实验装置探究：（1）“电流产生的热量跟电阻大小是否有关”；（2）“电流产生的热量跟电流大小是否有关”；改实验装置是分别将阻值已知的电阻丝放入完全相同的两个杯子中，然后在两个相同的U型管中装入水，再将U型管接入杯中密封（密封的空气质量相同且此时U型管内水面相平）。若通电一段时间后，电阻丝产生的热量使密闭空气膨胀，U型管中水面高度将发生变化，此变化反映了密闭空气温度的变化。探究（1）中，他们将两电阻串联到电源两端；探究（2）中将两电阻分别接到电压不同的电源两端，通电相同的时间后，实验现象如图（a）、（b）所示。

阅读下列短文，从每题所给的四个选项(A、B、C和D)中，选出最佳选项。

B

    Our risk of cancer rises as we age. So it makes sense that the elderly should be routinely screened for new tumors(肿瘤)—or doesn't it?

    While such careful tracking of cancer is a good thing in general, researchers are increasingly questioning whether all of this testing is necessary for the elderly. With the percentage of people over age 65 expected to nearly double by 2050, it's important to consider the health benefits of screening and the costs of routine testing.

    In many cases, screening can lead to additional operations to remove cancer, which can cause side effects, while the cancers themselves may be slow-growing and may not cause serious health problems in patients' remaining years. But the message that everyone must screen for cancer has become so ingrained that when health care experts recommended that women under 50 and over 74 stop screening for breast cancer, it caused a strong reaction among doctors, patients and advocacy(拥护) groups.

    It's hard to uproot deeply held beliefs about cancer screening with scientific data. Certainly, there are people over age 75 who have had cancers detected by routine screening, and gained several extra years of life because of treatment. And clearly, people over age 75 who have other risk factors for cancer, such as a family history, should continue to get screened regularly. But for the remainder, the risk of cancer, while increased at the end of life, must be balanced with other factors like a remaining life expectancy.

    A recent study suggests that doctors start to make more right decisions about who will truly benefit from screening—especially considering the explosion of the elderly.

    It's not an easy guess to make, but one that makes sense for the whole patient. Dr. Otis Brawley said, "Many doctors are ordering these tests purely to protect themselves against medical disputes(纠纷). We need to think about the good use of health care and stop talking about the rationing(定量配给制) of health care."

    That means making some difficult decisions with elderly patients and going against the misguided belief that when it comes to health care, more is always better.