The question was: Where would you look to find out if the corrected t value is significant?
Your Answer: Under Mean diff
Answer and explanation: Your answer is incorrect. The correct answer is: "Under Sig. (2-tailed)."
You would look in the first row of the column "Sig. 2-tailed" and find that the probability value is less than 0.001. The effect is therefore significant. The "Mean diff" is the mean difference. It does not tell whether or not the value is significant.