据相关研究，经过40min完全黑暗后，人眼对光的敏感性达到最高点，比黑暗前增加25000倍，将数据25000用科学记数法表示为（ ）
【解析】
【分析】科学记数法的表示形式为a×10n的形式，其中1≤|a|＜10，n为整数．确定n的值时，要看把原数变成a时，小数点移动了多少位，n的绝对值与小数点移动的位数相同．当原数绝对值大于或等于10时， n是正整数；当原数的绝对值小于1时，n是负整数．
【详解】解：将数据25000用科学记数法表示为2.5×104，
故选：B．
【点睛】此题考查科学计数法，科学记数法的表示形式为a×10n的形式，其中1≤|a|＜10，n为整数．
The family ___ at the lunch table when someone came to tell them what had happened at ___.
I called you just now, but you weren't in. Sorry, I ______ the reading room.
I will give ______ students ______ minutes for them to finish their exercise
Every morning, WE are asked ______ taken our temperatures.
She ______ his number in the phone book to make sure that she had got it right.
I will spend as much time as I ______ the lesson.
He's never stolen anything before, ______ he? ______. It's his third time to be taken to police station.
Has Jack finished his homework yet? I've no idea, But he ______ it the whole afternoon.
______did you sleep last night? I was reading too late to fall asleep.
Have you ______ your father recently? No. He doesn't often write to me.
