对市场调查的分析与评估，主要是考察市场调查的有效性。有效的市场调查应具备的特点包括(

已知数列{a_n}是各项均为正整数的等比数列，数列{b_n}是等差数列，且a₆=b₇，则有（　　）

A．a₃+a₉≤b₁+b₁₀

B．a₃+a₉≥b₄+b₁₀

C．a₃+a₉≠b₄+b₁₀

D．a₃+a₄与b₁+b₁₀的大小关系不确定

如果线段a=2，c=4，且b是a和c的比例中项，则b²=______．

请根据句意或括号中的中文提示、英文释义，写出句中所缺单词，使句子通顺。

小题1:I was good at all the ________________ except physics when I was at school. I still think it is difficult now.

小题2:As a host, she has many duties, but her main job is to _________ (介绍) the pop stars.

小题3:Don’t run _____________ (穿过)the road when the traffic lights are red. It’s dangerous.

小题4:Nowadays, some people become ___________ (unable to hear at all) because of noise pollution.

小题5:Most students feel ________ (tired and unable to relax) and angry from time to time because their parents are strict with them.

承揽受电工程施工的单位应具备哪些资质？

个体化药物治疗存在药学和医学两个领域的认识区别，分别称为药学认识和医学认识。

医学认识和药学认识共同强调的因素是（）

A.患者的个体差异因素

B.患者本身的生物遗传因素

C.药物的体内暴露

D.药物效应

E.药物的分子生物学评价