The different paths have different levels of difficulty.

VOA: special.2009.12.09

Engineers have found that wetlands, grassy fields and soil or sand filters can take in stormwater with different levels of pollution and release water with a relatively constant cleanliness.

VOA: standard.2010.08.04

In place of steps, a ramp goes round and round past the art on the different levels.

VOA: special.2009.04.06

The shape of a snow crystal may change from one form to another as the crystal passes through levels of air with different temperatures.

VOA: special.2010.01.05

They are based on levels of damage to twenty-eight different kinds of structures and other objects.

VOA: special.2011.04.19