The invertebrate's first line of defense is
A: skin.
B: mucus membranes.
C: exoskeleton.
D: secretions.
A: skin.
B: mucus membranes.
C: exoskeleton.
D: secretions.
举一反三
- All of the following are part of the first line of defense against invaders except A: tears B: saliva C: neutrophils D: skin
- ________To do a skin test, a doctor puts venom under the skin.
- A bluish-purple discoloration of skin and mucous membranes usually resulting from a deficiency of oxygen in the blood is termed ____.
- Choose the correct answers according to the pictures.[img=428x520]18031ea2d6f09e0.jpg[/img] A: He has freckled skin and a round face. B: He has winkled face and tanned color skin. C: He has rosy cheek and silky skin. D: He has dry skin and fair complexion.
- Moat is the second line of defense to prevent the enemy attack. （）