【多选题】下列有关艾滋病预防的措施,正确的是:
A.
遵守性道德,避免高危性行为,是预防经性途径传播艾滋病毒的根本措施。
C.
对感染艾滋病病毒的孕产妇及时采取抗病毒药物干预,减少产时损伤性操作,避免母乳喂养等预防措施,可大大降低胎儿、婴儿被感染的可能性。
D.
要避免与艾滋病患者的血液、精液、乳汁等体液直接接触
【单选题】When did her mother put Christmas presents in her stockings?
【简答题】有一半径为R的均匀带电球体,电荷体密度为+ρ,今沿球体直径挖一细隧道,设挖隧道前后其电场分布不变,如图所示。现在洞口处由静止释放一点电荷-q,其质量为m,重力在此忽略不计。试分析点电荷在隧道内的运动规律。
【单选题】---When is Christmas? --- It’s _____ December 25.
【判断题】赫希曼—赫芬达尔指数越大,市场竞争程度越高。( )
【单选题】人类从单纯获取天然产物转变为开始种植农业发生在大约公元前()左右。
【单选题】When Christmas Day is coming, the parents .
A.
usually tell their children that Father Christmas isn't real
B.
sometimes tell their children that Father Christmas comes during the day
C.
tell their children that Father Christmas comes during the night and brings presents to good children
D.
often tell their children that Father Christmas gives presents to poor children
【单选题】In 'LoveActually', Harry is not happy with ()when he is doing Christmas shopping with his wife.
【单选题】四企业集中程度越高,行业内的竞争性_________;赫芬达尔一赫希曼指数越大,行业内的竞争性_________。
E.
这个问题的前提是错误的,因为四企业集中率只适用于市场内只有四家企业的市场,根据定义,这样的市场是没有竞争性的