In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to calculate a ph [title] Know what ph actually is. [step] The ph is the concentration of hydrogen ions in a solution. A solution with a high concentration of hydrogen ions is acidic. <sep> (A) A solution with a low amount of hydrogen ions is basic, or also known as alkaline. Hydrogen ions, also known as hydronium, are written shorthand as h or ho. (B) A solution with a lower concentration of hydrogen ions could produce a ph requiring constant testing. [substeps] One of the very most common ph disorders in medical terminology is macular degeneration. (C) Being aware of that fact can help you calculate the ph of your solution. [title] Create a ph chart to use for tracking the concentration. (D) A ph that is lower than zero may indicate a ph imbalance. A ph imbalance can be caused by both chemical reactions or a combination of both.
A