A protostar forms once the nebular cloud condenses and the core begins to heat. To heat is the answer hope this helps you!!
Pretty sure the correct answer is D
<span>Physical weathering is a term used in science that refers to the geological process of rocks breaking apart without changing their chemical composition. Over time, movements of the Earth and environment can break apart rock formations, causing physical weathering.</span>
A vaccine is a preparation of one or more microbial antigens to induce protective immunity in potential hosts.
Vaccines are the anti-microbial agents administered to provide immunity against specific diseases. There can be a wide variety of vaccines, like: live attenuated vaccine, vaccine with killed or inactivated microbes, vaccine containing the sub-parts of the microbes, etc.
Immunity is the body's ability fight against a disease. The immunity is build when a body gets attacked by pathogen. Various immune cells like neutrophils, MHCs, dendritic cells, B and T cells, etc. are involved in building and strengthening the immunity of any person.
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It is known as structurlism