单选题：阅读材料，回答题：My Life at Renda1 learned very quickly that being

阅读材料，回答题：
My Life at Renda
1 learned very quickly that being a teaching assistant (TA) at the University of Iowa would be differen from a teacher at Renmin University_______(46) Eyes staring, mouths open, students examining my big nose, hands nerv0us,people whispering while I wrote my name on theblackboard.
At Iowa, when my first classes began, half my students still hadn't arrived. When everyone finally found a seat, ringing cellphones and loud yawns (哈欠) interrupted my opening remarks. It is not that American students were disrespectful. ______ (47) They were, however, far more skeptical than the students I had at Renda. The truth is I couldn't fault them for their skepti- cism. Undergraduates at large US universities--especially freshmen and sophomores--often have several classes a semester handled by TAs. In some. cases, the TA sets the course content. ______ (48) Most have good intentions, but only a few are as effective as flesh-and-blood pro- fessors.
Every teacher has to confront obstacles to learning--no matter what the culture. Students who talk during lectures, students who cheat, students who question the grade they get for a paper or project dealing with these is all part of the job. ______ (49)
The difference, I think, is that in the US I had to swallow more of my pride.______ (50) I had a responsibility to teach them, of course, but I had to do so indirectly as a guide who himself had a few things to learn from the students.
A．Back at Renda, I had walked into my first classes feeling like a celebrity.
B．In my students' minds, I had little to offer them, except perhaps some sample questionsfor the mid-term exam.
C．In others, the TA works as a grader and discussion leader.
D．I encountered these in China, and I faced them in the US.
E．On the other hand, being taught by a graduate student is not necessarily bad.
F．Most were polite, or at least, indifferent.
请回答（46）题