Antibiotic such as penicillin blocks

An example of antibiotic medicine :

Which one of the following is an antibiotic drug?

Which one of the following statements is correct about effects of antibiotics on viruses ?

An antibiotic is not useful against a virus whereas a vaccine is. Which one of the following is the most appropriate reason for this ?

Name a clinical trial in which blood is transfused from recovered COVID-19 patient to a coronavirus patient who is in critical condition.