One of the challenges of studying life from ancient times is that not all organisms form fossils. Which of the following explains why some organisms form fossils and others don't. (Select all that apply)

a. The tracks or burrows of an organism must be filled with sediments before they are disturbed.

b. The organism must first get stuck in rock.

c. The soft tissue of the dead organism must be eaten by scavengers or decomposers before the bones can be preserved.

d. The organism's body must be covered by sediment or another substance before its body decays.

do yall know the answer?

when the displaced particles are perpendicular to the direction the wave travels, is called a transverse wave, whereas in longitudinal wave the displace practices are parallel to the direction of the wave.

in the given image:

first image shows - longitudinal wave

second image shows - transverse wave

third image shows - longitudinal wave

fourth image shows - longitudinal wave

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blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.