与实在社区相比，虚拟社区具有哪些特征：（）。 A.交往的超时空性 B.人际互动具有匿

阅读理解。

       One day when Jack was walking in the park, he saw Sue, a friend of his, sitting on a bench with a dog beside her. The dog was looking up at Sue.

       Jack walked up to her and said, " Hello, Sue. How are you? May I sit and talk with you for a while?"

        "Of course. Please sit down," Sue said. Jack sat down next to Sue on the bench, and  they talked together. The dog went on looking at Sue. It seemed that it wanted some food.

     "That's a nice dog," Jack said, pointing at the animal. "Yes, he's handsome. He's strong and healthy. "

      "And hungry," Jack said. "He hasn't taken his eyes off you.  He thinks you've got some food for him. "

      "That's true,"  Sue said. " But I haven't. "  The two friends laughed and then Jack said, " Does your dog bite?"

      "No," Sue said. "He's never bitten anyone. He's always gentle and good-tempered. "

        Hearing this, Jack decided to pet the dog. He  put up his hand and touched the animal's head. At

once it jumped up and bit him. "Hey!" Jack shouted, "You said he didn't bite. "

      "No, I didn't," Sue answered. "You asked me if my dog bit, and I said no.  But that's not my dog. My dog's at home. "

根据短文内容判断正误，对的在括号中写T，错的在括号中写F。

(       )1. Jack and Sue didn't know each other before they met in the park.

(       )2. Jack asked to sit down next to Sue because he wanted to have a rest.

(       )3. Jack thought that the dog belonged to Sue.

(       )4. Sue's dog had never bitten strangers.

(       )5. The dog in the park wasn't gentle and good-tempered.

若关于x的方程x²﹣4x+m=0没有实数根，则实数m的取值范围是

A．m＜﹣4

B．m＞﹣4

C．m＜4

D．m＞4

Who ____________ they? [ ]

A. am

B. is

C. are

国际市场环境调研的主要内容

大气数据仪表给机组提供（）

A.飞机的高度和指示空速（IAS）

B.飞机的高度和指示空速（IAS）的备用指示

C.飞机的高度，空速和位置

D.以上都不对