【单选题】内因子是由以下哪一种细胞所分泌? ( )
【单选题】某些媒分子通过使环绕肺气管的骨肉细胞收缩来抵御有毒气体对肺部的损害。这使得肺部部分封闭起来。当这些媒分子被不必要的激活时,对某些无害的像花粉或家庭粉尘作出反应,就出现了哮喘病。 有一项计划是开发一种药物通过阻碍接收由上文所说的媒分子发出的信息来防止哮喘病的发生。以下哪一项,如果是正确的,将指出这项计划的最严重的缺陷?
A.
研究人员仍不知身体是如何产生这种引发哮喘病的媒分子的。
B.
研究人员仍不知是什么使一个人的媒分子比其他人的更易激活。
C.
很多年内无法获得这样的药物,因为开发和生产这种药物都需要很长的时间。
D.
这样的药物无法区分由花粉和家庭粉尘引发的信息与由有毒气体引发的信息。
E.
这样的药物只能是预防性的,一旦得上哮喘,它无法减轻哮喘的程度。
【简答题】—It’s a long time since I saw my sister. —__________ her this weekend? A.Why not visit B.Why not to visit C.Why not visiting D.Why don’t visit
【单选题】The reason why Arizona is short of stewards is that______.
A.
more major corporations are moving out of state than moving in
B.
it lacks the right environment required for nurturing qualified leaders
C.
there is something seriously wrong with is education
D.
the state leadership is not adequately represented by different ethnic groups
【单选题】The fact _______ he does so in so short period of time challenges explanation. A why
A.
44 . The fact _______ he does so in so short period of time challenges explanation. A why
【简答题】For this part, you are allowed 30 minutes to write a short essay entitled Why Are There Fewer Students in the Library. You should write at least 150 words following the outline given below: 1. 学校图书馆利用...
【判断题】由于人们在文化习俗、个人习惯等方面存在差异,所以基本的身体语言讯号还是有着很大的差异。()
【单选题】---Why is the little boy crying over there? -----He is too short to reach ___ the toy bear ___ the toy car on the shelf?