I/O点数为256点以下的为小型PLC。

把二次函数y=x²-4x+1化成y=a（x-h）²+k（其中h、k是常数）的形式的结果为（　　）

A．y=（x-2）²-3

B．y=（x-4）²-15

C．y=（x-2）²+3

D．y=（x-4）²+15

A 21-year-old primigravida has an emergency cesarean delivery under general anesthesia because of unanticipated fetal distress. One postoperative intervention is to assist her to turn every 2 hours. Which of the following conditions is this intervention intended to prevent ？（）

A．Pressure ulcers.

B．Muscular stiffness.

C．Respiratory complications.

D．Venous stasis.

姜半夏的功能主要是（）

A.长于化痰

B.长于降逆止呕

C.长于消肿散结

D.长于燥湿化痰

E.偏于祛寒痰，调和脾胃

下面程序的功能是把文件file1.txt中重复字符去掉后(即若有多个字符相同,则只保留1个)写入文件 file2.txt。请填空。Private Sub Command1_Click()Dim in char As String,temp As String,out char As StringOut char=""Open"file1.txt"For Input As#1Open"file2.txt"For Output As【 】n=LOF( 【 】) in char=Input$(n,1)For k=1 To ntemp=Mid(in char,k,1)If InStr (out.char,temp)= 【 】ThenOut char=out char＆tempEnd IfNext kPrint #2, 【 】Close #1Close #2End sub

（）是指基因突变后有时能回复到突变前的状态。

A.正突变

B.逆突变

C.回复突变

D.野生型