Most inspired particles such as dust fail to reach the lungs because of the .a. ciliated mucous lining of the upper respiratory tractb. abundant blood supply to nasal mucosac. action of the epiglottisd. porous structure of turbinate bones

so many dust particles are there in the air. during inhalation, those particles fail to reach our lungs due to the presence of ciliated mucous lining in our upper respiratory tract.  

primarily nose and its ciliated mucous lining and nasal hair prevent the dust particle to come inside. if some particles get entry then the person starts sneezing until those particles are out.  

if the nose fails to prevent the dust then our respiratory tract does it.

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

the answer is c) an oak tree