定义名为“姓名”元素，该元素的内容不允许为空，下面正确的选项是（ ）。 A: <element name="姓名" required="true"/> B: <element name="姓名" required="false"/> C: <element name="姓名" nillable="true"/> D: <element name="姓名" nillable="false"/>

利用DTD给“公民”元素定义名称为“身份证号”的属性，该属性取值唯一且不可缺省，下面哪个选项（ ）正确？ A: <!ATTLIST 公民 身份证号 ID B: REQUIRED> C: <!ATTLIST 公民 身份证号 IDREF D: REQUIRED> E: <!ATTLIST 公民 身份证号 ID F: IMPLIED> G: <!ATTLIST 公民 身份证号 ID H: FIXED>

The electric furnace is used extensively to produce the high-grade steel _____ for the manufacture of steel alloys. A: to be required B: requiring C: required D: that required

To apply for the position, applicants _____ to create an online account. A: required B: are required

For profile controls, datums are: A: Allowable but not required B: Not allowed C: Required D: No answer

I am sure Mary has been here and （） A: did what required her B: has done what required her C: has done what was required of her D: did what has been required of her

The boss required ________.

As he ——to submit the according report before 4:30 p.m., the assistant hurried to Mr. Smith’s office. A: was required B. had required C. requires D. required

比较化合物乙酸（Ⅰ）、乙醇（Ⅱ）、苯酚（Ⅲ）、碳酸（Ⅳ）的酸性大小（ ） A: Ⅰ>Ⅲ>Ⅱ>Ⅳ B: Ⅰ>Ⅳ>Ⅲ>Ⅱ C: Ⅰ>Ⅱ>Ⅳ>Ⅲ D: Ⅰ>Ⅲ>Ⅳ>Ⅱ

化合物①对甲基苯酚,②对甲氧基苯酚,③对三氟甲基苯酚,④对溴苯酚,⑤苯酚酸性强弱顺序正确的是( ) A: ③>④>>⑤>②>① B: ④>③>>⑤>①>② C: ③>④>>⑤>①>② D: ②>①>⑤>④>③