How would you proceed?

You are trying to break into a highly classified top-secret mainframe computer with highest security system in place at Merclyn Barley Bank located in Los Angeles. You know that conventional hacking doesn’t work in this case, because organizations such as banks are generally tight and secure when it comes to protecting their systems. In other words you are trying to penetrate an otherwise impenetrable system.
How would you proceed?

A.
Try to conduct Man-in-the-Middle (MiTM) attack and divert the network traffic going to the Merclyn Barley Bank’s Webserver to that of your machine using DNS Cache Poisoning techniques

B.
Look for “zero-day” exploits at various underground hacker websites in Russia and China andbuy the necessary exploits from these hackers and target the bank’s network

C.
Launch DDOS attacks against Merclyn Barley Bank’s routers and firewall systems using 100,000 or more “zombies” and “bots”

D.
Try to hang around the local pubs or restaurants near the bank, get talking to a poorly-paid or disgruntled employee, and offer them money if they’ll abuse their access privileges by providing you with sensitive information