Which of the following is one of the best password security practices?

a$.$ Always keep strong but easy$-$to$-$remember and easy$-$to$-$guess password, Keep same password for multiple accounts

b$.$ Always keep strong but hard$-$to$-$remember and easy$-$to$-$guess password. Never use same password for multiple accounts

c$.$ Always keep strong but easy$-$to$-$remember and hard$-$to$-$guess password. Never use same password for multiple accounts

d$.$ Always keep strong but hard$-$to$-$remember and hard$-$to$-$guess password. Keep same password for multiple accounts