Answer:
Hard
Explanation:
it is hard because these are usually hard parts of an organism including shells, bones, teeth, woody trunk, stems, and branches.
The oxygen molecules moves through the nostrils, pharynx, trachea, bronchus, smaller and smaller branches of the bronchial tree, and then into the alveolus.
Chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name, and it contains no words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulas can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than are chemical names and structural formulas.
C) As the trait will then pass to others without it and through natural selection will become abundant
