Please choose the correct ending to complete the given sentence: Computers and Electronics: [header] How to test the acidity of your rain [title] Gather the necessary materials. [step] For this experiment, you will need to collect some rain water and get some strips of ph paper. Ph paper is a special type of paper that changes color based on how acidic or basic a solution is.

Ending1: River banks are the best places to find ph paper. Testing water for ph can be expensive and will require significant research. Ending2: [substeps] There are two sizes of ph paper you will need for this experiment. Ph paper has a diameter of 3 to 4 inches. Ending3: [substeps] These test strips are available at different labs or at online testing facilities. You can purchase ph paper at your local academic library. Ending4: The paper comes with a separate color chart that allows you to identify the ph according to the color. [substeps] Ph paper can be purchased at gardening or pool stores.

Answer format: ending1/ending2/ending3/ending4