题干

同时掷2枚硬币,2枚硬币都是正面朝上的可能性是(  )

A:12

B:13

C:14

D:15

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答案(点此获取答案解析)

C

同类题1

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

      Both men and women are livinglonger these days in industrialized countries.____Ingeneral, they can expect to live six or seven years more than men. One reasonfor this is biological.

      One important biological factor thathelps women live longer is the difference in hormones between men and women.____Between the ages of about 12 and 50,women produce hormones that are involved in fertility(生育能力). These hormones also have a positive effect on the heartand blood flow. In fact, women are less likely to have high blood pressure orto die from heart attacks.

       ____Theyhelp the body defend itself against some kinds of infections. This means thatwomen generally ger sick less often and less seriously than men. The commoncold is a good example: women, on average, get fewer colds than men.____ Scientists are still not exactly sure howinfluence aging, but they believe that they do. Some think that a woman's bodycells have a tendency(向) to age more slowly than a man's. Others think that a man's body cells have a tendency to age more quickly.____

A.However,women, on average, live longer.

B .The biological factorplays an important part.

C. Women are also helped bytheir female genes.

D. The female hormones alsoprotect the body in another way.

E. Recent research seems tosupport both of these possibilities.

F. Therefore, women are morehealthy than men and can live a better life.

G. Hormones are chemicalswhich are produced by the body to control carious body functions.

同类题4

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    Ask any kid, and you'll likely hear that time spent with friends is the coolest and most important part of the school day. Educators, as well, acknowledge that making friends is one of the most valuable things children do as they learn and grow. But many parents are perplexed by their children's social lives, wondering how to help their kids cope with the challenges, heartbreaks, and the joys of making friends, losing them, and making friends again.

    “Friendships help children gradually learn to be independent, contributing members of a community and it's just as important as their academic growth” notes Diane Levin, Ph.D., author of “Remote Control Childhood.” However, it's a slow process. There are many social skills to learn, which advance with age and experience, trial and error, and experiencing the satisfaction that comes from contributing to an ongoing friendship.”

    “Friendship starts as soon as children can crawl off their parents' laps over to another child,” adds Michael Thompson, Ph.D., co-author of her life with you to her life with her friends. but who their friends are, how they interact with them, and how popular they are, is something parents have only limited control over.”

    Experts on children's behavior say that problems like jealousies, breakups, bullying and teasing account for a big part of what parents, kids and teachers talk about, and what parents worry about.

    Get insights into how children's friendships develop and how parents can help, if needed, and find ways to determine if your child is at risk for serious social problems or simply suffering from real (but common) social challenges.