During a network investigation, Alfred, a cybersecurity analyst, identifies two key irregularities: The CEO, who tends to work late, logged in from both Paris and Tokyo within five minutes, and there's an unexpected surge in emails from the HR department outside of recruitment season. Which of the following should the analyst be MOST concerned about based on these observations?

A$.$

The absence of the CEO's usual late$-$night login

B$.$

Simultaneous login from distant locations

C$.$

A recent software update on the CEO's computer

D$.$

The sudden increase in emails from the HR department