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问题 单项选择题 A3/A4型题

胎盘是母体与胎儿间进行物质交换的器官，是胚胎与母体组织的结合体。

每个胎盘有()

A．100个胎儿小叶

B．100～200个胎儿小叶

C．200个胎儿小叶

D．300个胎儿小叶

E．400个胎儿小叶

答案

参考答案：C

选择题

设计方案可行，且化学方程式书写正确的是（　　）

A．实验室用稀硫酸与铜片反应制取氢气：Cu+H2SO4=CuSO4+H2↑

B．用盐酸除去氢氧化钾溶液中的碳酸钾：K2CO3+2HCl=2KCl+H2O+CO2↑

C．用含氢氧化铝的药物治疗胃酸过多症：Al（OH）3+3HCl=AlCl3+3H2O

D．用稀硫酸除铁锈：Fe2O3+H2SO4=FeSO4+H2O
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A How to Use a Painting Knife 使用画刀的方法
Painting with a knife is a bit like putting butter on bread and produces quite a (1) result to a brush. Painting knives are excellent for producing textured, impasto work and (2) areas of flat colour.
What’s the difference between a palette knife and a painting knife
A palette knife is a long, straight spatula that is used (3) mixing paints and scraping a palette clean. They’re made from metal, plastic, or wood and (4) either be completely straight or have a slightly bent handle. A painting knife has (5) large crank in the handle, which takes your hand away from the painting surface. They (6) in numerous shapes(for example pear-, diamond-, or trowel-shaped) and are used for painting (7) of a brush. The edge of the knife is blunt, so that it doesn’t cut the (8) .
·What shape of painting knife should I use
Different shaped painting knives produce different effects. For example, a short blade produces angular strokes (9)a long blade makes it easy to put down sweeps of colour.
·Why can’t I use a palette knife to paint with
You can. Painting (10) just have the advantage of coming in more angular shapes and with sharper points. And (11) larger crank in the handle means there’s less chance of rubbing your knuckles into wet (12) . If you’re unsure whether you’re going to enjoy painting with a knife, first buy a (13) , plastic palette knife and experiment a bit with this before upgrading to a wood-and-metal knife.
·How do I use painting knife
(14) the handle firmly so you’re got good control. Pick up some paint off your palette (15) the tip, as you’d pick up some butter with a knife. Use the side of the (16) to spread paint across your canvas, or press it onto the canvas, as you (17) spread butter across a slice of bread．It’ll seem strange at first as it’s quite (18) to using a brush. Using just the tip of the blade will produce small dots. (19) the edge of the knife down will produce fine lines. Pressing the blade flat down (20) the paint will produce ridges. Scrape back into the paint to reveal underlying layers (called sgraffito).

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