What are the key cells in an allergy attack?
Options:
- (A) layers of fat
- (B) Lymphocytes.
- (C) fur and fat
- (D) bone cells
- (E) muscle cells
- (F) the skin
- (G) Red blood cells
- (H) animals
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Let's think first: Lymphocytes are the key cells involved in the immune response. An allergy attack is an immunal response. Lymphocytes are the key cells involved in an allergy attack.... So the answer is [(B)]

What die quickly if a stroke occurs?
Options:
- (A) a fish
- (B) animals
- (C) brain cells
- (D) organs
- (E) critical organs
- (F) protons
- (G) neutrons
- (H) bones
--
Let's think first: Brain cells die quickly if their oxygen supply is cut off. If the oxygen supply to the brain is cut off, a stroke can occur. Brain cells die quickly if a stroke occurs.... So the answer is [(C)]

The most ancient what are trees with woody trunks?
Options:
- (A) it needs them
- (B) leafy greens
- (C) more abundant
- (D) Leeuwenhoek
- (E) flowering buds
- (F) pollen
- (G) graptolites
- (H) seed plants
--
Let's think first: Most modern gymnosperms are trees with woody trunks. Gymnosperms are the most ancient seed plants. The most ancient seed plants are trees with woody trunks.... So the answer is [(H)]

What causes h20 to expand when frozen?
Options:
- (A) evaporation
- (B) vaporization
- (C) hydrogen bonds
- (D) helium bonds
- (E) mysterious forces
- (F) nitrogen bonds
- (G) Physical weathering
- (H) precipitation
--
Let's think first: Hydrogen bonds cause water to expand when it freezes. Water is everywhere H20. Hydrogen bonds cause H20 to expand when it freezes.... So the answer is [(C)]

What is used as energy by most organisms?
Options:
- (A) sodium
- (B) water
- (C) energy.
- (D) food
- (E) sugar
- (F) Energy
- (G) solutes
- (H) light
--
Let's think first: Glucose is used for energy by the cells of most organisms. For instance, glucose is a sugar. Sugar is used for energy by the cells of most organisms.... So the answer is [(E)]

Arthropods have a life cycle with what?
Options:
- (A) rapid expansion
- (B) survival
- (C) aerobic capacity
- (D) food and shelter
- (E) an organism's body
- (F) reproduce
- (G) barnacles
- (H) mixing genes up
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Let's think first: Arthropods have a life cycle with sexual reproduction. Sexual reproduction mixes the genes up more than is possible with asexual reproduction. Arthropods have a life cycle with mixing genes up.... So the answer is [(H)]