Task: Class Definition Understanding (ontology: Earth_Environment/SWEET)

Which of the following definitions best describes 'ph'?

A. the concept refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. The term combines the words ‘feldspar’ and ‘silica.’ the concept minerals are usually light in color and have specific gravities less than 3. Common the concept minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars. The most common the concept rock is granite. On the opposite side of the rock spectrum are the iron and magnesium-rich mafic and ultramafic minerals and rocks. [Wikipedia]
B. In physical geography, the concept is an area where the tree growth is hindered by low temperatures and short growing seasons. There are two types of the concept: Arctic the concept (which also occurs in Antarctica), and alpine the concept. In the concept, the vegetation is composed of dwarf shrubs, sedges and grasses, mosses, and lichens. Scattered trees grow in some the concept. The ecotone (or ecological boundary region) between the the concept and the forest is known as the tree line or timberline.
C. The movement of salt water into fresh water aquifers.
D. the concept is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions (H+). Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations. The the concept scale is not an absolute scale; it is relative to a set of standard solutions whose the concept is established by international agreement. [Wikipedia]

Answer: the concept is a measure of the acidity or basicity of a solution. It is defined as the cologarithm of the activity of dissolved hydrogen ions (H+). Hydrogen ion activity coefficients cannot be measured experimentally, so they are based on theoretical calculations. The the concept scale is not an absolute scale; it is relative to a set of standard solutions whose the concept is established by international agreement. [Wikipedia]