Decreasing returns to scale may arise from ______.A．specialization of inputs.B．duplication

Which of the following may hardness of the boiler water cause？ （1) scale formation; （2) tube failure; （3) corrosion.

（) offer great advantages to ocean freights, such as economy, safety and large scale？A.

How is the weight used？A．To measure amounts of rainfall.B．To check the accuracy of scales.

Care must be taken to condition the ______ in the boiler to prevent scaling, and corrosion

What do astronomers use photographic plate for？A．Decreasing the time it takes to photograp

The phrase“this scale”in paragraph 6 refers to___