| a. | Skin |
| b. | Macrophages and T-helper cells |
| c. | HCI in stomach |
| d. | Secretion of lacrimal glands |
| (a) | All parasites are pathogens as they cause harm to the host. |
| (b) | Pathogens have to adapt to live within the environment of the host, |
| (c) | Pathogen of amoebic dysentery lives in the gut of host organism. |
| (d) | Pathogens can enter human body by various means causing functional damage but do not interfere with normal vital activities. |
| 1. | Vaccine prepared by traditional method |
| 2. | Antigens present in the body of humans |
| 3. | Memory of the immune system |
| 4. | Site of interaction between antigen and antibody |