1.optical adj. 光学的;眼睛的,视觉的
Sloping walls on the bulk of the building create an optical illusion.
大楼主体的斜墙给人造成一种视错觉 。
2.fertilizer n. [肥料] 肥料;受精媒介物;促进发展者
The tractor hauled the fertilizer away.
拖拉机把肥料拉走了 。
3.navigation n. 航行;航海
Pack ice around Iceland was becoming a threat to navigation.
冰岛周围的浮冰一度成为船舶航行的威胁 。