As an AI language model, I cannot provide a personal opinion. However, both biology and computer science can be challenging for students in class 9 depending on their interests, skills, and learning abilities. Biology involves the study of living organisms, their structure, function, and interactions with each other and their environment. On the other hand, computer science deals with the theory, design, and applications of computer systems, software, and programs. Some students may find one subject harder than the other, but it ultimately depends on individual preferences and strengths.
