Do 1a, 1c and 3a you very much! : d

1 a. viruses, bacteria, fungi, protozoa, and worms. 
1 c. This would indicate that the hosts had some kind of immunity to the pathogen, it's not harmful, the pathogen is weak, or the pathogen does not attack the host
3 a. Infectious diseases are spread through coughing, sneezing, physical contact, exchange of body fluids, contaminated water or food, or through zoonosis.
I hope this helps you!!