When many muscles contract a little bit, simultaenous, it produces:
Options:
- (A) forces
- (B) heat
- (C) cold blooded
- (D) sweat
- (E) electrical energy
- (F) Energy
- (G) pain
- (H) thermal displacement
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Let's think first: Shivering occurs when many muscles contract a little bit all at once. Heat production is increased by shivering and non-shivering thermogenesis . Heat production is increased when many muscles contract a little bit, all at once.... So the answer is [(B)]

What breathes by relaxing the lungs?
Options:
- (A) mammals
- (B) tortoises
- (C) dogs
- (D) chickens
- (E) ducks
- (F) humans
- (G) crocodiles
- (H) animals
--
Let's think first: Mammals breathe with the help of a diaphragm. Belly breathing uses the diaphragm, which helps relax the lungs. Mammals breathe by relaxing the lungs.... So the answer is [(A)]

What has radial symmetry?
Options:
- (A) peachleaf willow
- (B) sea urchins
- (C) humans
- (D) gastropod shells
- (E) A Greek letter
- (F) asymmetry
- (G) dogs
- (H) Most plants
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Let's think first: Adult echinoderms have radial symmetry. Sea urchins are echinoderms, in the same family as starfish. Adult sea urchins have radial symmetry.... So the answer is [(B)]

What creates active immunity from a parasite?
Options:
- (A) Cooking
- (B) memory cells
- (C) alpacas
- (D) peachleaf willow
- (E) Allergies
- (F) mammals
- (G) an organism's body
- (H) animals
--
Let's think first: Active immunity results when an immune response to a pathogen produces memory cells. If the parasite causes harm, it is a pathogen. When a parasite produces memory cells, active immunity results.... So the answer is [(B)]

What can be determined by the average number of people per one unit of area?
Options:
- (A) hygeine
- (B) emissions
- (C) animals
- (D) growth
- (E) forces
- (F) health
- (G) education
- (H) people
--
Let's think first: Population density is the average number of individuals per unit of area or volume. Another measure of growth is population density. Growth of an area can be determined by the average number of people per unit of area.... So the answer is [(D)]

Antigens are molecules that prompt the what of antibodies?
Options:
- (A) termination
- (B) failure
- (C) humans
- (D) decrease
- (E) production
- (F) anemia
- (G) rapid expansion
- (H) kinetic
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Let's think first: Antigens are molecules that the immune system recognizes as foreign to the body. Antigens prompt the body to produce antibodies. Antigens are molecules that prompt the production of antibodies.... So the answer is [(E)]