The answer to this is D. For those who do not know, a sodium hydroxide relaxer is known to be useful in making the hair straighter because this can help break down the bonds of the hair. This is something that can be used by professionals and can be applied to people who would like to have straighter hair.
Straight hair is considered to be more manageable as compared to natural wavy or curly hair. It is recommended that only professionals will use this relaxer because if a beginner or a novice use this, it might damage the hair. There is also a big possibility that it may result in hair loss when used the wrong way.