Lymphocytes secrete a protein which causes the dilation of blood vessels. The protein is

$Pseudomonas$ $cola$ causes:

Consider the following statements:
$I.$ People should get vaccinated to avoid infection.
$II.$ Vaccination is available against polio,cholera,typhoid,tuberculosis,and many other diseases.
$III.$ Eradication of vectors is necessary for diseases like malaria and filariasis.
$IV.$ Dengue and chikungunya are both spread by $Culex$ mosquitoes.
Which of the statements given above are correct?

The branch of medicine which is associated with the diagnosis,prevention,and treatment of mental disorders is:

Who discovered the vaccine for smallpox?

How was the "good humor" hypothesis of health disapproved?