Charlie studied in a famous college for four years． He studied hard and did well in all his subjects． He hoped to become a good teacher． This year he left the college and began to work in a middle school． He likes his students and is strict（严格的） with them． He does his best to make his classes lively and interesting．
One day he carefully explained a chemical reaction（反应） to the students of Grade 2 in the chemistry lab．
“Be careful， everyone，” he said loudly． “Before I make the experiment，there're twenty five atoms of carbon（碳原子），but after I finish it， there're twenty four atoms of carbon left！”
He stopped to watch the classroom and hoped his students would go on explaining it． But the young men looked at each other and nobody answered him． He had to ask， “What happens？ What makes the atom lost？”
The classroom was very quiet and none of the students looked at their teacher．
“Who can tell us where it has gone？”
Suddenly a soft voice came from the back row， “We did not see anybody leave the lab！”
1．Charlie began to work in the middle school because ＿＿＿＿＿＿＿．
A．he had been in the school for four years B．he couldn't do anything except teaching
C．he hoped to become a good teacher D．he did well in all his subjects
2．Charlie hopes ＿＿＿ ，so he does his best to make his classes lively and interesting．
A．all his students could understand him B．his students wouldn't be afraid of him
C．his students carefully watched him making the experiment
D．his students could do well in chemistry
3．That day Charlie wished ＿＿＿＿＿＿＿ ．
A．his students could learn the chemical reaction
B．his students could find the atom of carbon
C．his students could count（数） the atoms of carbon
D．his students could make the experiment
4．The students couldn't answer Charlie's questions because ＿＿＿＿＿＿＿ ．
A．none of them had seen the atoms B．they didn't understand their teacher
C．the chemical reaction was too complicated D．they all wanted to drop the subject
5．In fact，＿＿＿＿＿＿＿ ．
A．Charlie failed that day B．the student in the back row didn't watch her teacher carefully
C．the student in the back row hadn't learned chemistry before
D．Charlie failed in making the experiment