The question asks to find the percentage of candidates who failed in at least two subjects. From the four options, the correct answer is option 1 which is 7.8

Starting with option 1 (7.8), this answer is correct as the data would suggest that approximately 7.8% of the 500 candidates failed in at least two subjects.

Next, option 2 (0.078) is not correct. It`s incredibly low and it would mean that fewer than one in a thousand students failed in at least two subjects, which doesn`t seem plausible given the question.

Then, option 3 (6.8) is also not correct. This would mean that a lower proportion of candidates failed in at least two subjects than option 1 (7.8).

Finally, option 4 (1.0) is not correct. This would mean that only 1% of students failed in at least two subjects, which is too low compared to the data provided in the question.

In conclusion, option 1 (7.8) is the most plausible answer that would reflect the percentage of the students who failed in at least two subjects.