Nelson received a call from someone claiming to be a bank representative. He told Nelson that since his credit card was soon to expire, it needed to be reactivated. He asked for Nelson's credit card details, which Nelson gave him readily. A few hours later Nelson received an email stating that a purchase worth $1250 had been charged to his credit card. Which of these kinds of cyber-attacks is Nelson a victim of?

a) A ransomware attack
b) A hoax
c) A spam
d) A phishing email