The number of students who scored at least 8 in a quiz means,the total number of students that scored 8 marks and above
The number of students that scored 8 marks from the dot plots is

The number of students that scored 9 marks from the dot plot is

The number of students that scored 10 marks from the dot plot is

Therefore,
The number of students who scored at least 8 in a quiz will be

Hence,
The final answer is OPTION C