Which of the following is a sign that wax has cooled and thickened too much?

When wax cools and thickens too much, it becomes hard and unusable. This characteristic makes it difficult to apply effectively. The ideal consistency of waxing products is important for achieving smooth application and effective hair removal. When the wax hardens, it can no longer adhere properly to the hair or skin, resulting in ineffective waxing and potential discomfort for the client.

Other signs associated with wax include bubbling, which usually indicates overheating rather than cooling; a strong smell, which may arise from the ingredients in the wax but does not specifically relate to its thickness; and the ability to spread easily, which signifies the wax is at an appropriate warmth and consistency for application. Therefore, the indication that the wax has cooled and thickened too much is clearly its hardness and unusability, which is why this choice is the most accurate.