已知P是⊙O内一点，⊙O的半径为15，P点到圆心O的距离为9，则通过P点且长度是整数的弦的条数是（    ）

下列是生物生殖和发育有关的示意图，其分析正确的是（  ）

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    How to improve your English speaking skills?Here are some tips.

    Find native English speakers.Talking to actual native speakers is the most effective way to improve your English skills.Your progress will be greater if you use this way.

    Slow down. If you want to be understood,slow down.If you speak more clearly,your listeners can understand you better.

    Record yourself.Though we hear ourselves all the time,we don't quite know what we sound like.So record yourself!And then you can focus on what you need to improve.

    Take different classes.One class is good.But if you can take more than one class—of different styles—that's even better.

    Speak English at home.Make a plan to speak it at home.Talk to yourself in English.You can also narrate your actions.While you're washing the dishes,say what you're doing,thinking,or feeling.It keeps your brain thinking in English.

    Create opportunities.English speakers are everywhere.You have to find them. You can call up an English hotline.Call a phone company and make small talk about phone plans.Start a blog.Get into English chat rooms.There are ALWAYS opportunities to be found.