题目

阅读理解请阅读下列短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑。A Day school ProgramSecondary students across Toronto District School Board(TDSB) are invited to take one or two e-Learning courses on their day school timetable. Students will remain on the roll at their day school.The on-line classroom provides an innovative relevant and interactive Learning environment. The courses and on-line classroom are provided by the Ministry of EducationThese on-line coursesare taught by TDSB secondary school teachersa3．下列属于该河河口形成的地貌是（　　）A．沟谷B．瀑布C．冲积扇D．三角洲