They are a layered structure located between paired homologs in prophase i of meiosis in many organisms. they are required for moving homologs to opposite sides of the poles during anaphase i of meiosis. they are required for moving sister chromatids to opposite sides of the poles during anaphase ii of meiosis and anaphase of mitosis. they catalyze the phosphorylation of specific proteins. they are important for maintaining homologous chromosome pairing and plays a role in recombination. they are filaments in mitotic and meiotic spindles.

answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]

the earth is thought to have been formed about 4.6 billion years ago by collisions from a cloud of hydrogen, helium, rock, ice and other materials. these were pulled together by gravity to form objects in and around earth like- asteroids and small early planets called planetesimals.

so, the best possible answer to this question will be option d- to harden materials to form different parts of earth’s layers