题干

生男生女主要取决于()的类型。

A:受精卵

B:精子

C:卵细胞

D:生殖细胞

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答案(点此获取答案解析)

B

同类题2

阅读下面科普短文(本文由网络文章改写)。
松花蛋又称皮蛋、变蛋、灰包蛋等,因剥开蛋壳后胶冻状的蛋清中常有松针状的结晶或花纹而得名,是一种我国传统风味食品,口感鲜滑爽口,色香味均有独到之处。中医认为,松花蛋性凉,对牙痛、眼痛等疾病有一定疗效。由于松花蛋会有一股碱涩味,在吃松花蛋的时候可以加入少量的姜醋汁。
松花蛋是用料泥包裹鸭蛋、鸡蛋等加工而成。料泥是由生石灰、纯碱、食盐、红茶、草木灰(主要成分K2CO3)等原料与水按比例混合均匀制得。料泥制作过程中,通过一系列反应,产生的强碱(NaOH、KOH)经蛋壳渗入到蛋清和蛋黄中,与其中的蛋白质作用,致使蛋白质分解、凝固并放出少量硫化氢气体和氨气。同时渗入的碱还会与蛋白质分解出的氨基酸进一步发生中和反应,生成的盐的晶体沉积在凝胶态的蛋清中,便出现了朵朵“松花”。而硫化氢气体则与蛋清和蛋黄中的矿物质作用生成各种硫化物,使蛋清和蛋黄的颜色发生改变,蛋清呈特殊的茶褐色、蛋黄则呈墨绿色。下图表示松花蛋腌制时间与其中蛋清和蛋黄的pH的变化关系。

很多人在平时生活中都非常喜欢吃皮蛋瘦肉粥、凉拌松花蛋,专家提醒这种食物少吃无妨,却不能过多食用。其一,松花蛋腌制过程中蛋白质分解、变质,导致营养价值遭到了一定的破坏。其二,市售松花蛋还可能含铅(国家规定松花蛋中铅含量需小于0.5 mg/kg)。微量铅很容易被儿童吸收,导致铅中毒。其三,剥开皮的松花蛋1至2小时内一定要吃完,若长时间暴露在空气中,非常容易感染沙门氏杆菌,沙门氏杆菌会快速繁殖,此时食用松花蛋很容易引起中毒现象。
依据文章内容,回答下列问题。

同类题4

阅读理解

    A “virtual (虚拟的) cocktail” glass that lets you change the flavor (味道) of your drink using your Smartphone has been developed by scientists.

    Offering a customizable (定制的) range of drinks and tastes, the Vocktail can change a glass of water into a cocktail at the press of a button. The world's first technology tricks your brain into thinking it is experiencing a specific flavor by fooling your senses of sight, smell and taste.

    Developed by researchers at the National University of Singapore, the glass' three sensory components are controlled via a Smartphone App. Because the software can combine a number of smells, colors and tastes, the Vocktail can create almost any flavor.

    Developer Nimesha Ranasinghe said: “Our approach is to increase drinks flavor experience by overlaying outer sensory stimuli (刺激物). For example, in the Vocktail we overlay color, taste and smell sensations to create an adjustable flavor experience. Flavor is mainly how we feel food and that is achieved through the use of these senses. Therefore, by changing the color of the drink, using different smells and changing the taste through electricity, we are able to copy the flavor of a drink without it actually changing the liquid.”

    The glass houses three fragrance containers connected to micro-air pumps. The pumps release smell that change your feeling of the drinks, flavor. For example, a lemon fragrance will trick your brain into believing it is tasting lemon-flavored drink.

    On the outside edge of the glass are two electrode strips (电焊条) that send electric pulses into your tongue to stimulate your sense of taste and flavor differs with different pulses.