What is the only sedimentary rock type that can be formed from things that were once alive

Astudent observes a star from two positions of earth in its orbit, in summer and winter, and measures the change in the position of the star. which of these can be best calculated by this method?

~fourth largest plate ~includes parts of the indian and atlantic oceans ~subducts below the eurasian plate on the west side ~ the arabian and somali plates form boundaries with it what is the name of the tectonic plate described above? a) african plate b) eurasian plate c) north american plate d) indo- australian plate

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.