How do you determine the strongest$/$weakest oxidizing agent without using the table of standard reduction potential. Let$$s look at two specific examples.

$1.$ Determine the weakest oxidizing agent:

a$.$ HNO$3$

b$.$ HClO$4$

c$.$ H$3$PO$4$

d$.$ O$3$

The answer is choice C

$2.$ Determine the strongest oxidizing agent:

a$.$ Al$3+$

b$.$ Ag$+$

c$.$ Au$3+$

d$.$ Cu$2+$

The answer is choice C

In terms of OA strength, I understand that increasing O$.$N$.($to a more positive value$)$ increases OA strength. Additionally, I understand that increasing electronegative increases OA strength.

For Q$1$: When comparing answer choices a$,$ b$,$ c $$ Cl has an O$.$N$.$ of $+7$ compared to an O$.$N$.$ of $+5$ for N and P$.$ Therefore, HClO$4$ is the strongest of the three being compared because it has the highest O$.$N$.$ on the most electronegative atom. Likewise, HNO$3$ is a stronger OA than H$3$PO$4$ because N is more electronegative than P$.$ Overall, I understand why H$3$PO$4$ is the weakest OA$.$ However, I do not know how to compare, or rather tell which molecule is a stronger OA $$ HClO$4$ or O$3?$

For Q$2$: I am completely lost at how to determine that AU$3+$ is the strongest OA$.$ Other than the fact that it has a $+3$ O$.$N$.$ compared to the others. But then again, so does Al$.$ So why is Au$3+$ a better OA than Al$3+?$ Does it have to do with electronegativity?

For both of these questions a table of standard reduction potentials was NOT given. That is why I would like to know how to come to the conclusion without having to look at one.