Iron ore, the main raw material of steel, changed the lakes area and the nation.

VOA: special.2009.11.11

So you pick a better material like iron and steel, that makes a better bridge, we know that now because we have experience with bridges, but still your bridge might fail.

你选择了钢铁作为材料,来造了一座更好的桥,我们现在能够明晰这一点,是因为在造桥这件事上我们现在很有经验,但即使是我们现在造的桥也仍然会倒塌

耶鲁公开课 - 生物医学工程探索课程节选

So you pick a better material like iron and steel, that makes a better bridge, we know that now because we have experience with bridges, but still your bridge might fail.

你选择了钢铁作为材料,来造了一座更好的桥,我们现在能够明晰这一点,是因为在造桥这件事上我们现在很有经验,但即使是我们现在造的桥也仍然会倒塌

耶鲁公开课 - 生物医学工程探索课程节选