Which structures are part of the body's first line of defense against pathogens?

a. mucous membranes

b. lymph nodes

c. white blood cells

d. red blood cells

A. Mucous membrane.

Explanation:

Mucous secrete mucus. When any pathogen tries to enter into the human body, the mucous snares those pathogens and prevents them from entering into the human body. As an example: Nasal hairs help to remove or fight against suspended micro-organisms when they are present in the air and try to enter into the nose. Cilia is a small type of hairs that beat to force mucous to the pharynx for swallowing into the stomach.

the two answers are a, the population of birds with large beaks will increase on the island, and c, the trait for large beaks will be passed on to future generations through natural selection. the reason for that is because if the birds that have beaks developed for eating small seeds lose all of their food, they will go hungry and eventually starve because they physically cannot eat the large seeds, therefore making the population of large beaked birds higher. also, if the trait of large beaks are dominant on the island over small beaks, then over time the large beaked birds will reproduce more and more, while the smaller beaked birds will reproduce less and less because they can't survive with the food provided. that leads to the trait of small beaks disappearing and the trait of large beaks taking over the island.