The correct answer is A.

The $5^{\text{th}}$percentile of$Q_i(t)$is plotted to the `$5^{\text{th}}$ percentile of the standard normal distribution. This is because the Gaussian default time copula, as represented by the equation, maps the cumulative default probabilities of an asset at a given time to the univariate standard normal distribution on a percentile-to-percentile basis. This means that each percentile of the cumulative default probabilities corresponds to the same percentile of the standard normal distribution. Therefore, the $5`^{\text{th}}$ percentile of $Q_i(t)$ would indeed be mapped to the $5^{\text{th}}$ percentile of the standard normal distribution.

Choice B is incorrect. The Gaussian default time copula maps the percentiles of $Q_i(t)$ to the same percentile of the standard normal distribution. Therefore, the $4^{\text{th}}$percentile of$Q_i(t)$would be mapped to the `$4^{\text{th}}$, not $5`^{\text{th}}$, percentile of the standard normal distribution.

Choice C is incorrect. The mapping in a Gaussian default time copula is on a percentile-to-percentile basis, meaning that each percentile in $Q_i(t)$ corresponds to the same percentile in the standard normal distribution. Thus, it's not accurate that $5^{\text{th}}$percentile of$Q_i(t)$would map to `$3`^{\text{rd}}$.

Choice D is incorrect. The statement incorrectly suggests that there's a mismatch between percentiles when using Gaussian default time copula for mapping – this isn't true as it maps on a like-for-like basis i.e., each specific percentile in one distribution corresponds directly with same specific percentile in another.