$\frac{5}{2}$应该标在直线上的哪个位置？（　　）

已知函数f（x）=（ $\left(\sqrt{3}\sin \frac{\omega }{2}x+\cos \frac{\omega }{2}x\right)\cos \frac{\omega }{2}x-\frac{1}{2}$ cos $\frac{\omega }{2}x-\frac{1}{2}$ （ω＞0）的最小正周期为2π

（Ⅰ）求ω的值；

（Ⅱ）在△ABC中，角A、B、C的对边分别是a，b，c，且满足（2a﹣c）cosB=bcosC，求函数f（A）的取值范围．

    Is it difficult for you to get up in the morning? Are you often late for work or school? Yes? Then a scientist called Mike has a special bed for you. His Bed will get you up in the morning! Here is how it works!

    The bed is connected to an alarm clock. First, the alarm clock rings. You have a few minutes to wake up. Next, a tape recorder in the bed plays soft music and then your girlfriend's beautiful voice comes, “Wake up, darling, please.” A few minutes later, loud music comes from the tape recorder. At the same time, you may hear the voice of your boss. Your boss shouts angrily, “ Wake up at once, or you'll be late!” If you don't get up after that, you'll be sorry! A plastic “foot” is in the bed. It kicks you in the head. Then the bed waits for a few more minutes. What! You're still in bed! Slowly the top of the bed rises higher and the foot of the bed goes lower. Finally, you fall off the bed and onto the floor. You are out of the bed and awake!

    Mike made his bed because he wanted to take part in a competition. Mike won one of the top prizes for his bed.

    Yesterday was ____.In the morning, it was rainy, so I didn't____out. I studied ____ and cleaned my bedroom. Then I used my computer and played games. In the afternoon, it was____.I visited my good friend Lisa. We____some tasty food. Then we read some____.We____a good time together.

司马迁的《史记·三代世表》中仅记录了夏商周各王的名字，而没有在位的具体年代，这种状况被称为(    )