【简答题】二次曲线 ,当a 值取 ,曲线为椭圆型曲线;当a 值取 ,曲线为双曲型曲线;当a 值取 时,曲线为抛物型曲线.
【单选题】Why does the woman mention the information in the poster?
A.
To point out that the tour leader's name was not listed.
B.
To point out a problem with the student's suggestion about walking to the gallery.
C.
To explain why so few students signed up for the trip.
D.
To explain why the bus would not be available for taking the students on the trip.
【单选题】h1至h6标签可定义标题,其中h1 定义( )
【单选题】教师不直接将学习内容提供给学生,而是为学生创设问题情境,引导学生去探究和发现知识和问题的方法是( )。