The Correct Answer is: D. 1,2,4
Answer:
A. maintenance of axons is not a cellular activity associated with microtubules.
Explanation:
Microtubules are hollow, bead-like, tiny tubular structure that helps cells maintain its shapes. Together with microfilaments and intermediate filaments, they form part of the cell's cytoskeleton. Microtubules also contributes to the cell movement or cytokinesis that includes muscle contractions in muscle cells. Microtubules also replicated chromosomes to opposite ends of a cell during cell division. Microtubules also contribute to the parts of the cell that help it move and are structural elements of cilia, centrioles and flagella. A bundle of microtubules makes up an axonemal structure of cilia and flagella.
The Precambrian eon is separated from the Phanerozoic eon in the fossil record because of the sudden appearance of organisms.
Explanation:
Precambrian eon is the initial existence on earth that can be predicted by the study of rocks and remaining of fossils. It has been seen as the existence of skeleton in this era, before this era no such things has been observed, even the development of sexual reproduction.
The Phanerozoic era comes after the Precambrian era, more advanced kinds of fossils of animals had been observed in this era. Phanerozoic era period of life on earth. Large organisms sudden appearance are seen in the Phanerozoic era i.e. First dinosaurs, mammals, fishes, angiosperms,first vertebrates etc.
The rigth answer is D.
The wavefront or wavefront is an equal phase surface of a wave, i.e., these points have the same travel time from the source. The concept is used to describe the propagation of waves such as sound or electromagnetic radiation (light, radio waves, etc.). In a homogeneous and isotropic medium, in which the waves propagate without deformation, two types of particular waves are distinguished according to whether the wavefronts are spheres (spherical wave) or planes (plane wave).
All of the above is the answer
