The quick response of the immune system to a second infection is due to the _____, a feature of the immune system as demonstrated by the success of vaccines
a. activation of macrophage cells
b. suppression of suppressor cells
c. T and B memory cells
d. high levels of antigen
e. new cytotoxic T cell.
c
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Trees are able to transport water from the roots to the top branches because
A. cohesion bonds water molecules to each other strongly. B. liquid water has a higher density than the air in the plant cells of the roots, trunk, and branches. C. water acts as a solvent of the tree cells as it moves upwards to the branches. D. adhesion bonds water molecules to the inside of the plant conducting tubes. E. leaves are hydrophilic.
The amount of dissolved oxygen in the water is an important factor used to assess the health of a lake. What is the relationship between the temperature of the water and the concentration of dissolved oxygen?
A) Cooler water temperatures prevent oxygen from being dissolved in the water. B) Warmer water temperatures decrease the amount of oxygen that can be dissolved in the water. C) Water temperature does not affect the amount of oxygen dissolved in the water. D) Warmer water temperatures increase the amount of oxygen that can be dissolved in the water.
A bacterial cell, a plant cell, and an animal cell have which of the following structures in common?
a) cell wall b) nucleus c) cytoplasm d) nucleoid e) vacuole
In a woody stem, the vascular cambium is located directly below the outer bark
1.True
2.False