The correct answer is: A. Some students are not bright.
The statement “All students in my class are bright” is a universal affirmative statement. This means that it is a statement that applies to all members of a group. In this case, the group is “students in my class.” The statement says that all members of this group are bright.
The statement “Manish is not bright” is a particular negative statement. This means that it is a statement that applies to a specific member of a group. In this case, the group is “students in my class.” The statement says that one member of this group is not bright.
The statement “Some students are not bright” is a particular affirmative statement. This means that it is a statement that applies to some members of a group. In this case, the group is “students in my class.” The statement says that some members of this group are not bright.
The statement “Manish must work hard” is a modal statement. This means that it is a statement about what is possible or necessary. In this case, the statement says that it is possible or necessary for Manish to work hard.
The statement “Non-bright ones are not students” is a false statement. This is because there are many people who are not bright who are still students.
Therefore, the correct answer is: A. Some students are not bright.