搜题请搜索小程序“爱下问搜题”
问题 选择题

配制溶质质量分数一定的溶液，正确的操作顺序是（　　）

A．称量（量取）溶解、计算

B．溶解、计算、称量、（量取）

C．计算、称量（量取）、溶解

D．称量（量取）、计算、溶解

答案

配制溶质质量分数一定的溶液，首先要计算出配制该溶液需要的溶质和溶剂量，然后利用天平、量筒等仪器称量出所需要量的溶质和溶剂，最后把所取的溶质、溶剂倒入烧杯进行溶解．因此配制溶液的过程可概括为：计算-称量（量取）-溶解．

故选C

单项选择题

Melissa and LoveLetter made use of the trust that exists between friends or colleagues. Imagine receiving an （71） from a friend who asks you to open it. This is what happens with Melissa and several other similar email （72） . Upon running, such worms usually proceed to send themselves out to email addresses from the victim’s address book, previous emails, web pages （73） .As administrators seek to block dangerous email attachments through the recognition of well-known （74） , virus writers use other extensions to circumvent such protection. Executable (.exe) files are renamed to .bat and .cmd plus a whole list of other extensions and will still run and successfully infect target users.Frequently, hackers try to penetrate networks by sending an attachment that looks like a flash movie, which, while displaying some cute animation, simultaneously runs commands in the background to steal your passwords and give the （75） access to your network.

A．memory

B．caches

C．ports

D．registers
查看答案
判断题

现值指数是指将按照一定的贴现率，把项目投产后各年的净现金流量折算为投资初始日的现值合计，然后与原始投资额进行比较得出的差额（）
查看答案