下列DNA序列属于回文结构(palindrome)的是 A: ATGCCG TACGGC B: GGCCGG CCGGCC C: CTAGGG GATCCC D: GAATTC CTTAAG E: TCTGAC AGACTG

回文(palindrome)是指一个字符串从前面读与从后面读都一样,仅使用栈和队列,编写一个算法来判断一个字符串是否为回文。

回文是指正反相同的字符串，比如“123321”、“985589”就是回文写个 has_palindrome函数来检测一下所有的六位数，然后输出一下具备回文特质的数字，要求数字不能重复。

-Where is your father?-He ________ Australia and he ________ Sydney for two weeks. A: has been to;has been in B: has gone to;has been in C: has been in;has been to D: has gone to;has been to

10. With his hard work, John ____ the basic knowledge of computer.A. has caught B. has acquired C. has required D. has acknowledged A: A. has caught B: B. has acquired C: C. has required D: D. has acknowledged

—Where are the twins? —One ________ flowers and trees in the garden, the other ______ to help her. A: has watered, has gone B: is watering, has been C: is watering, has gone D: has watered, has been

John has never been on time, ( )? A: as John B: has not John C: has he D: has not he

He ____never ____ a problem with his boss. A: has ...has B: has ...had C: has ...have D: had ...had

What has happened to Bob A: He has retired. B: He has fallen ill. C: He has gone for a business. D: He has been late for work.

His grandma ______ for 5 years. A: has dead B: has died C: has been dead D: has been died