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在图中实线框所示的区域内同时存在着匀强磁场和匀强电场．一个带电粒子（不计重力）恰好能沿直线MN从左至右通过这一区域．那么匀强磁场和匀强电场的方向可能为下列哪种情况（　　）

A．匀强磁场方向竖直向上，匀强电场方向垂直于纸面向外

B．匀强磁场方向竖直向上，匀强电场方向垂直于纸面向里

C．匀强磁场方向垂直于纸面向里，匀强电场方向竖直向上

D．匀强磁场和匀强电场的方向都水平向右

答案

A、当匀强电场方向垂直于纸面向外，假设带正电，则电场力垂直纸面向外，若能做直线运动，则洛伦兹力须垂直纸面向里，则匀强磁场方向竖直向下，故A错误；

B、当匀强电场方向竖直向上，假设粒子带正电，则电场力也是竖直向上，而粒子从左向右运动，则要使洛伦兹力竖直向下，所以匀强磁场方向垂直于纸面向外．若粒子带负电，则电场力是竖直向下，要能做直线运动则洛伦兹力竖直向上，而粒子从左向右运动，所以匀强磁场方向垂直于纸面向外，故B正确；

C、当匀强电场方向竖直向上，假设粒子带正电，则电场力也是竖直向上，而粒子从左向右运动，则要使洛伦兹力竖直向下，所以匀强磁场方向垂直于纸面向外．若粒子带负电，则电场力是竖直向下，要能做直线运动则洛伦兹力竖直向上，而粒子从左向右运动，所以匀强磁场方向垂直于纸面向外．故C错误；

D、当匀强磁场和匀强电场的方向都水平向右，带电粒子不受洛伦兹力，因此在电场力作用下做直线运动，故D正确；

故选：BD

填空题

女性生殖系统中______是产生卵细胞的场所，受精卵在______中形成．
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单项选择题

Supporters of abortion rights held a lunch recently in honor of a momentous victory for their cause: 40 years ago, New York became the first state to fully legalize abortion. That 1970 law began to reduce the death and injury toll from back-alley abortions and set the stage for the Supreme Court’s Roe v. Wade decision in 1973, which made abortion legal nationwide and recognized a constitutional right to privacy.
But abortion-rights groups are newly anxious about new assaults on women’s reproductive rights, including a fight over abortion that snarled the last days of the health care reform debate. Anti-abortion groups are newly emboldened. Kelli Conlin, head of Naral Pro-Choice New York, told guests at the lunch that "anti-choice forces are mobilizing in every single state to limit a woman’s access to abortion in more insidious ways than we can imagine. "
As Ms. Conlin was speaking, members of the Oklahoma House were getting ready to override vetoes of two punishing abortion measures. The state’s Democratic governor, Brad Henry, rightly viewed these intrusions into women’s lives and decision-making as unconstitutional. One of the measures, which seems destined to spawn copycat bills in other states, requires women to undergo an ultrasound before getting an abortion and further mandates that a doctor or technician set up the monitor so the woman can see it and hear a detailed description of the fetus. The other law grants protection from lawsuits to doctors who deliberately withhold fetal testing results that might affect a woman’s decision about whether to carry her pregnancy to term.
Several states have either passed or are considering bills that would ban abortion coverage in insurance plans sold through the state exchanges established by the federal health care law. A new Utah law criminalizes certain behavior by women that results in miscarriage. Embarking on a road that could lead to the Supreme Court, Nebraska last month banned most abortions at the 20th week of pregnancy based on a questionable theory of fetal pain. About two dozen states are looking at bills to increase counseling requirements or waiting periods prior to abortions. About 20 states are considering new ultrasound requirements. "One in three women in this country will have an abortion in her lifetime, and yet we’re having exactly the same discussions and debates we were having forty years ago," Ms. Conlin said.
Anti-abortion forces aim ultimately to make abortion illegal. So far, by reducing the number of abortion providers, making insurance coverage more expensive and harder to get, and throwing up other obstacles, they have primarily succeeded in making it harder for women of modest and meager means to obtain a safe and legal medical procedure.
The painful decision to end a pregnancy should be made in private between a woman and her doctor—not in politically driven debate among members of Congress and state legislatures.

According to the author, the anti-abortion forces have done nothing but

A．spreading peril for women’s privacy and freedom.

B．increasing insurance coverage for pregnant women.

C．obtaining safe and legal medical procedure for women.

D．ending pregnant women’s pain in decision making.
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