An adolescent was diagnosed with primary syphilis. He has no known drug allergies. The most appropriate treatment would be:

a single dose of cefoxitin (Mefoxin) IM.

a single dose of benzathine penicillin G (Bicillin LA) IM.

cefaxitin (Mefoxin) IM weekly for 3 doses.

benzathine penicillin G (Bicillin LA) IM weekly for 3 doses.