Which of the following forms are available for lighteners?

The choice of cream, oil, and powder as forms of lighteners is correct because these forms are commonly used in hair coloring and lightening processes. Cream lighteners are often preferred for their ease of application and ability to stay in place during processing. Oil lighteners can provide a less damaging alternative, as oils can help to protect the hair while lightening. Powder lighteners are typically mixed with a developer and can provide a stronger lightening effect, making them versatile for different techniques.

The other forms listed in the other options, such as liquid, gel, foam, paste, or lotion, are not standard classifications of lighteners primarily used in barbering or hairdressing. While some of these may be used in specific applications or products, they are not the typical or most effective forms available specifically for lightening hair. Therefore, the selection of cream, oil, and powder aligns with the practices for effective hair lightening in the barbering industry.