题目内容：

As smog forced students to stay home, the online learning industry saw a sharp increase in consumers.

During the air pollution red alert from Dec. 8 to 10 last winter, the Beijing Commission of Education ordered all kindergartens, primary schools and middle schools to suspend classes (停课). But the commission urged that "teachers should guide students to make full use of digital materials and conduct online learning at home".

According to the China Education and Research Network, the number of new users of 17zuoye. com, an online homework platform, tripled (增至三倍) on Dec. 8 compared to the previous day.

Online courses companies also adopted special measures to meet students' demand for Internet learning during the red alert period. For example, New Oriental offered free online English classes for three days for school students as well as online question answering services.

Recent years have seen the popularity of online courses increase sharply in China. Massive Online Open Courses (MOOC), for example, originated in the United States but have become widespread in China since 2013. Some Chinese universities, including Tsinghua University and Peking University, have started their own MOOC platforms. "MOOCs have enlarged the time and space of teaching, fired up learners' interest, helped more people benefit from high quality educational resources and accelerated reform in many aspects of teaching," an official at the Ministry of Education told China Daily.

1.What were the teachers required to do during the red alert period?

A. Start MOOC platform.

B. Reform their way of teaching.

C. Work at home answering phones.

D. Guide students to learn via the Internet.

2.Who offered free online courses during the red alert?

A. The Ministry of Education.    B. New Oriental.

C. Tsinghua University.    D. Peking University.

3.The underlined words "fired up" in the last paragraph can be replaced by.

A. inspired    B. displayed    C. explained    D. destroyed

4.What may be the best title for the text?

A. Teach Online Courses

B. Take Measures, Stop Air Pollution

C. Stay Home, Get Online to Learn

D. Speed up Education Reform