What are the systematic names for each of the structures alkanes

Answer asap : ( a. how does mucus prevent the entry of pathogens? b. describe two ways white blood cells protect us from pathogens.

Which property of a rock remains unchanged by mechanical weathering? a. total surface area b. size and shape c. mineral composition d. sharpness

What effect would average population growth have on land usage? a. urban use of land would rise to more than 30 percent of available land. b. industrial use of land would rise to more than 30 percent of available land. c. the percentage of available land used as cropland would stay the same. d. cropland would fall to about 10 percent of available land.