List four preventive measures against communicable diseases.

You are aware of the $Polio$ $Eradication$ $Programme$ in your city. Children are vaccinated because:

Given below are a few situations:
$(i)$ Geeta of Class $IX$ was having a common cold. She sits with Sarika,who also develops the disease.
$(ii)$ Animesh of Class $IX$ shifted to a new residence with his family where a water purification system has not been installed yet. He develops Cholera and Dysentery.

$A$ person was bitten by a stray dog. After some days,his nature became irritated,and he started fearing water.
$(a)$ Name the disease.
$(b)$ Is there any vaccine plan available?
$(c)$ Is there any plan of your local authority for the control of this disease?

Making anti-viral drugs is more difficult than making anti-bacterial medicines because

$AIDS$ cannot be transmitted by: