C.To help the liquid behave normally.

D.To enable the water to move rapidly.

4.What is the author's attitude toward the idea of humans' walking on water?

A.It is risky but beneficial.

B.It is interesting and worth trying.

IC.t is crazy and cannot become a reality.

D.It is impractical though theoretically possible.

【考点】考察科普知识类阅读

【文章大意】人类一直都希望能够达到草上飞的境界。文章中叙述了使用cornflour在水面上产生一层，让我们能够在水上奔跑的新的理论，虽然在理论上可行，但是并不实际。

1.B 推理题。根据文章第2行：We simply weigh too much, and all our mass push down through our relatively small feet.可知我们人类太重 了，我们的身体把太多的重量都加到了我们的脚上，带来了太多的压力，让我们会沉下去。故B正确。

2.C 细节题。根据第二段第4行：The lizard will take as many as 20 steps per second to keep moving forward。可知这种蜥蜴可以在水面之上连续奔跑一段距离而不沉到水里。故C正确。

3.A 推理题。根据文章第三段第2,3行：you can create a "non-Newtonian" liquid that doesn't behave like normal water. Now ,if the surface of the water is hit hard enough ...可知这种cornflour会让水面上形成一个很厚的表层。故A正确。

4.D 推理题。根据文章倒数第三行Fun though all this may sound, it's still rather messy and better read about in theory than carried out in practice。可知这种做法仍然只是停留在理论上，并不能在实际上有应用。说明作者认为这是不实际的。故D正确。

【长难句解析】

1.By adding enough of this common thickening agent to water（and it does take a lot）, you can create a "non-Newtonian" liquid that doesn't behave like normal water.

【翻译】通过向水面添加一些这样的常见的东西，你会创造出一种不同于正常的水的非牛顿规律的液体。