Other countries were slow to follow suit not because they were stupid, sluggish or repressed, but because they did not have that particular combination of expensive Labour and inexpensive energy.
This refers to the combination of civil engineering design principles with plants and natural materials, such as rocks, which control erosion and slow-down the flow of water.
它既是将土木工程设计原理与植物和自然材料，如能够防止侵蚀并减缓水流的石材相结合。
3
The rusting of iron is the slow chemical combination of the elements of iron and oxygen in moist atmosphere.