La clase no es hay pocos alumnos. a. grande c. aburrida b. difícil d. inteligente

The sentence la clase no es grande. Hay pocos alumnos can be translated as the class doesn't have many people. There are few students. So the option grande is the more logical to be used here because we are describing that a class has few students, giving a negative answer about the class size at first.

de estos colores. sounds about right.