这里的however是什么意思It'shard（easy）formetodecidewhomIwillchoose,however,because（though）twostudents,DonaldandBrian,gotthesamegrade,为什么不能用括号里的原文Donaldwasnotverygoodatmath.Hecouldnotunde

Question

这里的however是什么意思
It's hard（easy） for me to decide whom I will choose,however,because（though） two students,Donald and Brian,got the same grade,为什么不能用括号里的
原文
Donald was not very good at math.
He could not understand the teather's explanations.
Even when the teather explained something a second time,Donald still could not understand it.
"Never mind,"Donald told himself."I'm quite good at other subjects.I'll cheat in the math exam,the I won't be in trouble.
"I'll sit next to the boy who's best at math,"he thought,"and copy down his answers."
The day of the exam came,and Donald sat next to Brian Smith,who always was at the top of the class in math.
Donald carefully copied Brian's answers on to his own exam paper.]
At the end of the exam ,the teacher collected the papers and graded them.
Then she said,"Well,boy and girls ,I've decided to give a prize to the student who got the highest grade.It's difficult for me to decide who to give the prize to,however,because two students,Donald and Brian,got the same grade."
"Let thenm share it,"one of the other student said.
"I've thought about that,"the teacher said,"but I've decided to give the prize to Brian."
Donald was angry when he heard this.
He stood up and said,"That's not fair .I got the same grade as Brian."
"That's true,"the teacher said."However,Brian's answer to Question 18 was‘I don't know.’yours was ‘Neither do I.’"

Answer 1

however是对上一句（I've decided to...)的转折,因为一般情况下最高分大家想当然只有一个,可现在不是.