下列关于体液免疫的叙述正确的是（）
A．有的抗原可以直接刺激B细胞，使其增殖分化成浆细胞
B．抗体是由B细胞分泌的
C．进行细胞免疫时，抗原不需经吞噬细胞的摄取和处理
D．效应T细胞可直接杀灭抗原
参考答案：A
解析：B细胞接受抗原刺激可能有两个途径，一是抗原直接刺激B细胞；另一方面是抗原经吞噬细胞、T细胞呈递给B细胞，故A正确；抗体是浆细胞分泌的，故B错；细胞免疫的感应阶段，抗原需要吞噬细胞的摄取和处理，故C错；体液免疫和细胞免疫都不能将抗原直接杀死，故D错。考点：本题主要考查体液免疫的调节，意在考查考生能理解所学知识的要点，把握知识间的内在联系，形成知识的网络结构的能力。
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| Everyone needs friends. We all like to _1 close to someone. It is nice to have a friend to talk, laugh and do things with. __2__sometimes we need to be alone. We don't always want people _3_ . But we could feel lonely if we never had a friend. No two people are just the same. Friends _4_ don't get on well. It doesn't mean that they no longer _5_ each other. Most of the time they will make up and become friends again. Sometimes friends move away. Then we feel very _6_ .We miss them very much, but we can _7 them and write to them. And we can make new friends. It is surprising to find out _8_ we like our new friends when we get to know them. There is more good _9 for people who have friends. They live longer than people who don't. Why? It _10_ be that they are happier. Being happy helps people stay well. Or it could be just knowing that someone cares. If someone cares about you, you take better care of yourself.
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