When a virus possesses an envelope, where did it get the envelope from?

Who first suggested the concept that viruses existed?

Which of the following tapeworm infections is associated with vitamin B12 deficiency macrocytic anemia: 

The fluke most commonly found in the US is:

A scolex is recovered in human feces after the patient is treated with medication. The scolex bears four cup-shaped suckers. This parasite is:

The nematode egg that appears as a barrel-shaped structure with clear polar plugs at each end of the egg belongs to:

The nematode Loa loa is transmitted to humans by

Paragonimus westermani infection is acquired by:

Based on the play “Fences” by August Wilson analyze how the concept of fences contributes to the themes of race relations, ambition, and family duty Rubric for grading: 25% Thesis statement guides readers and body development aligns with the thesis statement 25% One quote per body paragraph with parenthetical citation 25% Content is accurate and reflects the fact that the student has read the play 25% Grammar, spelling, punctuation, readability, etc.  Students are not allowed to use any pre-written notes or pre-written essays. Use of such will be considered suspect and the essay will be scored as a zero. The use of electronic devices is not allowed at any time during the exam. 

S.W. is placed on mechanical ventilation with PEEP settings adjusted to improve oxygenation. What is the primary purpose of PEEP in ARDS management?