主要用来切断介质通路,也可调节流量和压力的阀门是()。 ["球阀","疏水阀","截止阀","止回阀"]
public String makinStrings() { String s = “Fred”; s = s + “47”; s = s.substring(2, 5); s = s.toUpperCase(); return s.toString(); } How many String objects will be created when this method is invoked?() [" 1"," 2"," 3"," 4"," 5"," 6"]
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为什么清代幕僚盛行?
简述胶体的双电层结构
简述中外秘书接待来客的不同之处。