未知题型 上班时是否可以玩手机（）

未知题型 Write a complete paragraph with the topic sentence: With the development of science and technology, even students on campus begin to use mobile phones and view them as a must. Extend your paragraph with a number of supporting sentences and a concluding sentence. In your writing, the way you organize your sentences is supposed to help the readers to understand smoothly, using the techniques you have just learned in this class.

单项选择题 经期后几天可以使用产品呢（）