要读入8051MCU的I/O引脚的状态，需要先向IO寄存器的对应位写入 ，保证引脚内的MOS管是截止的，然后再读取（）
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A symbol can be（）
A. a picture
B. a short word
C. a single letter
D. a pair of letters
What is the main structure of a sentence（）
A. The SV construction
B. The SVO unit
C. The VO construction
D. The links
Why should we note the links on the left of the page（）
A. Because they are important
Because they are unimportant
C. Because they are both visible and readable
D. Because teachers want us to note like this
How should we note the SVO unit in note-taking（）
A. note it horizontally
B. note it vertically
C. note it vertically and hierarchically
D. note it in your own way
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