甲、乙、丙、丁4中物质分别含2种或3种元素，它们的分子中各含18

【名词&注释】

胡萝卜(carrot)、同系物(homologue)、氢化物(hydride)、次生木质部(secondary xylem)、质量比(mass ratio)、母细胞(mother cell)、次生韧皮部(secondary phloem)、孢原细胞(archesporial cell)、非极性键(nonpolar bond)、阴离子。

[单选题]甲、乙、丙、丁4中物质分别含2种或3种元素，它们的分子中各含18个电子。甲是气态氢化物，在水中分步电离出两种阴离子。下列推断合理的是

A. 某纳盐溶液含甲电离出的阴离子，则该溶液显碱性，只能与酸反应
B. 乙与氧气的摩尔质量相同，则乙一定含有极性键和非极性键^{(nonpolar bond)}
C. 丙中含有第2周期Ⅳ A族的元素，则丙一定是甲烷的同系物
D. 丁和甲中各元素质量比相同，则丁中一定含有-1价的元素

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学习资料：

[单选题]The term “multitasking” originally referred to a computer’s ability to carry out several tasks at one time. For many people, multitasking has become a way of life and even a key to success. In fact, some excellent mental aerobic exercises (大脑训练) involve engaging the brain in two or more challenging activities at a time. Although checking e-mail while talking on a phone and reading the newspaper may be second nature for some people, many times multitasking can make us less productive, rather than more. And studies show that too much multitasking can lead to increased stress, anxiety and memory loss.In order to multitask, the brain uses an area known as the prefrontal cortex (前额叶脑皮层). Brian scans of volunteers performing multiple tasks together show that as they shift from task to task, this front part of the brain actually takes a moment of rest between tasks. You may have experienced a prefrontal cortex “moment of rest” yourself if you’ve ever dialed (拨电话) a phone number and suddenly forgotten who you dialed when the line is answered. What probably occurred is that between the dialing and the answering, your mind shifted to anther thought or task, and then took that “moment” to come back. Research has also shown that for many volunteers, job efficiency (效率) declines while multitasking, as compared to when they perform. only one task at a time.

A. Multitasking is easiest when at least one of the tasks is habitual, or requires little thought. Most people don’t find it difficult to eat and read the newspaper at the same time. However, when two or more attention-requiring tasks are attempted at one time, people sometimes make mistakes.
B. We often don’t remember things as well when we’re trying to manage several details at the same time. Without mental focus, we may not pay enough attention to new information coming in, so it never makes it into our memory stores. That is one of the main reasons we forget people’s names---even sometimes right after they have introduced themselves. Multitasking can also affect our relationships. If someone checks their e-mail while on the phone with a friend, they may come off as absent-minded or disinterested. It can also cause that person to miss or overlook key information being passed on to them.
C. 49. Why are some mental aerobic exercises designed to engage people in multitasking?
D. To make them more productive.
E. To reduce their stress and anxiety.
F. To develop their communication skills.
G. To help them perform. daily tasks more easily.

[单选题]萝卜主要的食用部位为次生木质部，胡萝卜主要的食用部位为次生韧皮部^{(secondary phloem)}。( )

A. 正确
B. 错误

[单选题]花药发育过程中，单核花粉(即小孢子)形成的过程是( )。

A. 造孢细胞一孢原细胞^{(archesporial cell)}一花粉母细胞一小孢子
B. 花粉母细胞一孢原细胞^{(archesporial cell)}一造孢细胞一小孢子
C. 孢原细胞^{(archesporial cell)}一花粉母细胞一造孢细胞一小孢子
D. 孢原细胞^{(archesporial cell)}一造孢细胞一花粉母细胞一小孢子

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