Answer:
True
Explanation:
In phase-contrast objective and a phase contrast optical systems is equipped with Light microscope .
Phase contrast microscope is used to differentiate unstained structures in a cell that differ in refractive indices and thickness. Thus it is usefull for examining living unstained organisms.
Light that passed through materials of different refractive index and/or thickness will undergo a change in Phase. The difference in phase or wave front irregularities cause variation in brightness of the structures.
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Explanation:
To swim, they move their tails up and down, rather than back and forth as fishes do. This is because whales evolved from walking land mammals whose backbones did not naturally bend side to side, but up and down. ... Whales do the same thing as they swim, showing their ancient terrestrial heritage.
Cetaceans are fully aquatic marine mammals belonging to the order Artiodactyla, and branched off from other artiodactyls around 50 mya (million years ago). Cetaceans are thought to have evolved during the Eocene or earlier, sharing a closest common ancestor with hippopotamuses.
Answer:
you should always wash your hands regularly and avoidance of shaking hands