Good:
A, B1, C1, D1, E1
Of your choices, E1 is best.
"By" is not OK.
"Busy" is OK but sounds a little strange. Sounds like poetry or a newscast.
Also good:
"The streets are packed."
"The streets are packed with people."
"The streets are really crowded." (This is the best one, in my opinion.)
"The streets are really crowded with a lot of people."