若串s="MathTypes"，则其子串的数目是【 】。

阻塞性黄疸患者术前凝血酶原时间延长者，首先应用（）。

A.抑肽酶

B.血小板

C.维生素K

D.巴曲酶

E.新鲜冰冻血浆

It is easy for some people to learn a second language. However, others have difficulty in learning a new language. What can you do to help yourself learn a second language, such as English？__小题1:__

1．Feel positive about learning English.__ 小题2:__Be patient. You do not have to understand everything all at once. It is natural to make mistakes when you learn something new. We can learn from our mistakes. In other words, do not worry about making mistakes.

2．Practice your English. For example, write a diary every day. You will form a habit of writing it in English, and you will feel comfortable expressing your ideas in English.__ 小题3:__ In addition, you must speak English every day. You can practice with your classmates outside class.

3．__小题4:_You can write this in your journal. After each class, think about what you did. Did you answer a question correctly? Did you understand something the teacher explained? Perhaps the lesson was difficult, but you tried to understand it.

You must be positive about learning English and believe that you can do it. It is important to practice every day and make a record of your achievements.__ 小题5:__

A．Go over the points you have learned.

B．Keep a record of your language learning.

C．Don't give up when you meet some difficulty.

D．If you believe that you can learn, you will learn.E． Several weeks later, you will see that your writing is improving.

F． In these ways， you will enjoy learning English, and you will feel more confident in yourself.

G． There are several ways to make learning English a little easier and more interesting.

某历史学习小组为了探究“二战后资本主义世界经济体系的形成”查阅了大量的资料，其中符合这一探究主题的是

①布雷顿森林体系建立②国际货币基金组织建立

③《关税与贸易总协定》签署④北美自由贸易区正式建立[ ]

A．①②③

B．②③④

C．①③④

D．①②④

油罐清洗的周期是多长时间？

德国人（）首先创用了“浮游生物”一词。