根据对话内容选出可填入空白处的最佳答案，有两项为多余选项。 A：Hi, Emm

某企业生产某种商品的成本函数为C=a+bQ+cQ²，收入函数为R=ιQ-sQ²，其中常数a，b，c，ι，s都是正常数，Q为产量，求：

当税率为t时，该企业获得最大利润时的销售量；

阅读理解。

     Look at this boy. He is an English boy. His first name is Peter. His last name is Black.  His school ID

card number is three-two-eight-six-six-one-nine. His teacher is Miss Smith. Miss Smith is a good teacher. What's that? It's his backpack. It's blue. Where's his pencil-case? It's in his backpack.

根据短文内容，判断正（T）误（F）。

( )1. The boy is Peter Black.

( )2. His school ID card number is 3286699.

(     )3. His teacher's last name is Smith.

( )4. His backpack is black.

(     )5. His pencil-case is on the desk.

先化简，再求值：（2x+3）（2x-3）-8x（x-1）+（2x-1）²，其中x=1．

患者，男，18岁。口腔粘膜反复溃疡10年，又发作5天。检查所见：右侧舌缘圆形溃疡直径5mm，下唇内侧粘膜圆形溃疡直径3mm，溃疡周围有充血红晕，表面有黄色假膜。

估计患者本次发病的病程可能是（）

A.7～10天

B.10～20天

C.20～30天

D.30～60天

E.180天左右

启动水套加热炉后待炉温升至工况要求并高出约（）时，水套加热炉方可带负荷，投人生产保温。

A、10℃

B、15℃

C、20℃

D、25℃