Question

If foreign substances pass the body's first line of defense and into the bloodstream, what happens? They are attacked by saliva or mucous. They are attacked by lymphocytes. The body has no other defense.

Answer 1

the first line of defense in the body is through the skin and things like, tears, sweat, salvia that contain chemicals that can help fight pathogens, but only to a degree. if the pathogens are too strong, then they will get past this line of defense, which leads them to the next line of defense which are antigen specific lymphocytes. these lymphocytes are found in lymphoid tissues and will then multiply to fight invading pathogens. this means that the correct answer to your question is the second option, they are attacked by lymphocytes.
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Answer 2

The answer is that ~They Are Attacked By Lymphocytes~