Answer:
Intramuscular
Step-by-step explanation:
Intramuscular is a method of administering injection directly into the muscles for effective functioning.
Long acting penicillin are administered intramuscularly because of penicillin sensitive microorganisms that are subsceptible to low serum levels which is associated with penicillin dosage in the body and penicillin Has low level of solubility therefore it is slowly released into the muscles sites.