搜题请搜索小程序“爱下问搜题”
问题 选择题
函数f（x）=2 
1
x-3
的值域是（　　）
A．（-∞，3）∪（3，+∞）B．（-∞，1）∪（1，+∞）C．（0，+∞）D．（0，1）∪（1，+∞）
答案

令t=

1
x-3
，则t≠0
因为y=2t是指数函数，所以0＜2t≠20=1，
即0＜y且y≠1．
故选D．

阅读理解
阅读理解。
                                                           Beijing Library
To Susan Chan,
Just to remind you that you have 4 overdue books.
Title                                                              Author 
      Rose Meets Mr. Winter Garden          Bob Graham            due          22/1
      My Friend Whale                              Simon James           due          23/1
      Edward the Emu                               Sheena Knowles      due          24/1 
      Imagine                                            Alison Lester          due           25/1
Please return the books tomorrow. Other people may be waiting to borrow them. 
              Librarian Mrs. Josie Jones                   Date 3/2/2005
Note: You may not borrow any new books until these books have been returned.
1. This note was sent to _______.
[ ]
A. the librarian
B. Josie Jones
C. Alison Lester
D. Susan Chan
2. The book Imagine was written by _______.
[ ]
A. Alison Lester
B. Bob Graham
C. Simon James
D. Sheena Knowles
3. On what date was My Friend Whale due to be returned to the library?
[ ]
A. 22nd, January.
B. 23rd, January.
C. 24th, January.
D. 25th, February.
4. This note could be described as a _______.
[ ]
A. report card
B. news letter
C. reminder letter
D. set of instruction
5. From the note we can know that _______.
[ ]
A. Susan does not like reading
B. the library has many books to lend
C. someone else has borrowed these books
D. Susan may not borrow any new books at the moment
查看答案
单项选择题

下面是有关PC机性能的叙述，其中错误的是( )。

A．系统总线的传输速率对计算机的输入、输出速度没有直接的影响

B．高速缓存(cache)的功能是用来减少CPU等待的时间，提高系统速度

C．主存的存取周期是指从存储器中连续存取两个字所需要的最小时间间隔

D．系统的可靠性常用平均无故障时间(MTBF)和平均故障修复时间(MTTR)表示
查看答案