What are the chemical weapons involved with the first line of defense?
a. oil and sweat glands within skin
b. mucus and cilia lining the respiratory tract
c. saliva and digestive enzymes
d. all of these are correct

d. all of these are correct

Explanation:

Physical barriers are the first line of defense against invading agents. Examples of physical barriers include intact epithelia, the normal microbiota residing in these epithelia, and normal mucosal self-cleaning processes such as coughing, sneezing, mucus production, gastric acidity, vomiting, diarrhea, and urinary flow. All of these processes together make up a very efficient line of defense.

We can mention some members of the body's first line of defense, they are:

americans began to notice growing differences between the northern and southern sections of the country. there were more people living in cities in the north, which made it more urban. more people lived on farms in the south, which made it more rural. while many people were farmers in the northern states, there were now other ways to make a living, such as working in mechanical cotton gins factories manufacturing cloth, tools and other goods. people in the north supported high tariffs on goods imported from europe because the extra cost encouraged people to “buy american” instead. in the southern states, planters did not like tariffs because they sold most of their production to europe and bought their tools from there as well. southerners believed the protective tariff was something that only northern factory owners keep their profits high. so the southern politicians came up with an idea. they would opt out. they would simply ignore the protective tariff. it was ‘null and void’ in south carolina. the state would not collect the taxes on goods imported into south carolina, no matter what the president said they had to do. this decision led to the nullification crisis.