Which of the following merchant levels must scan the networks at least quarterly to be in compliance with PCI DSS$?$

Question $9$ options:

All merchants, no matter the size, must scan at least quarterly

Level $2(1$ million to $6$ million transactions a year$)$

Level $3(20,000$ to $1$ million transactions a year$)$

Level $1($more than $6$ million transactions a year$)$