Hello @Lucysrv18,
How are you doing? In this case, we know that Electromagnetic waves that are visible to the human eye is neither made up of two electromagnetic waves nor three. Therefore B and C is incorrect.
These electromagnetic waves are divided and they are our final two options. For sure, i can say that the wavelengths in a visible electromagnetic wave are not divided into nine, but instead it is divided into 7.
The answer to your question is A.
Thank you,
Darian D.