Answer:
Option D, Gastric Juices
Explanation:
The second line of defense is a non specific defense mechanism in which no specific individual is targeted but all invaders are killed in general way. Some common mode of second line of defense are - Phagocytic cells (white blood cells), inflammatory responses, macrophage system etc. The second line of defense comes into action when the invader has surpassed the first line of defense which include either physical barrier like skin, mucous membrane, hair, cilia etc. or chemical barriers like gastric juices, saliva, Hyaluronic acid etc.
Hence, gastric juice does not belong to second line of defense.
Thus, option D is correct.
Because it determines if it is isolated or not. This means if other substances can enter or not. This usually relies on the membrane with it´s pores. The pores help the membrane be selectively permeable in what it lets in and out.
<span>Looking at the two species' DNA would be a good place to start. If there are a number of similarities in their genotypes, then there would be a good chance that the two would also share some type of a common ancestor. This would be evidence that there was some type of selection that took place that necessitated two different species that shared a number of traits and features.</span>
So following the octet rule, carbon atom can only form a maximum of 4 bonds because, by then, it will have 8 valence electrons.
