飞机共有几个火井探测组件（FDU）（）A.1个； B.2个； C.3个。

设f（x）是一次函数，f（8）=15，且f（2）、f（5）、f（14）成等比数列，令Sn=f(1)+f(2)+…+f(n)，n∈N*，则S_n=______．

逻辑结构设计的阶段应考虑的主要因素是( )。

A．概念模式

B．存取方法

C．处理要求

D．DBMS特性

中国工农红军第一支坚强的队伍 ________________________________________

提高吸收效果有哪些可行措施？

Melissa and LoveLetter made use of the trust that exists between friends or colleagues. Imagine receiving an (16) from a friend who asks you to open it. This is what happens with Melissa and several other similar email (17) . Upon running, such worms usually proceed to send themselves out to email addresses from the victim’s address book, previous emails, web pages (18) .
As administrators seek to block dangerous email attachments through the recognition of well-known (19) , 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 (20) access to your network.

A．attachment

B．packet

C．datagram

D．message