Which equipment would be used to hold a small quantity of liquid for heating or reactions?

Test tubes are specifically designed to hold small quantities of liquids, making them ideal for heating or conducting chemical reactions. They are made from materials that can withstand heat and are shaped to facilitate mixing and observation of contents during an experiment. Their narrow cylindrical form allows for even heating when placed in a flame or water bath. Additionally, test tubes often come with a rack for stability during experiments, enhancing their practicality in laboratory settings.

In contrast, a spatula is used for measuring or transferring solid substances, a ruler is for measuring length, and a wash bottle is intended for dispensing water or other liquids, not for holding them during reactions. Thus, the qualities and intended use of test tubes make them the correct choice for this purpose.