The correct answer is: B. Acidic
Rainwater is slightly acidic because it dissolves carbon dioxide from the atmosphere to form carbonic acid. The pH of rainwater is typically between 5.0 and 5.6. This acidity can cause problems for plants and animals, and can also corrode metals.
Option A is incorrect because rainwater is not pure. It contains dissolved gases, minerals, and pollutants.
Option C is incorrect because rainwater is not toxic. However, it can be contaminated with pollutants, which can make it toxic.
Option D is incorrect because rainwater does not oxidize. Oxidation is a chemical reaction that involves the loss of electrons. Rainwater does not react with other substances in a way that causes them to lose electrons.