How are signs of a disease different from symptoms of a disease?

Priya's mother uses iodised salt at home. One day while cooking,Priya asked her mother about iodised salt. She said people who do not use iodised salt suffer from deficiency of iodine which leads to goitre and hypothyroidism.
$(a)$ What are the physical symptoms of goitre and hypothyroidism?
$(b)$ How will you inform others about the importance of iodised salt?
$(c)$ Is iodine a metal or a non-metal?
$(d)$ What are the physical properties of iodine?
$(e)$ What is the difference between iodised salt and normal salt?

Justify the following statements:
$(a)$ "Availability of proper and sufficient food would prevent infectious diseases."
$(b)$ "The general ways of preventing infection mostly relate to preventing exposure." List three points of prevention of exposure.

State whether the following statement is true or false:
Antibiotics commonly block biochemical pathways important for bacteria. However,viruses do not use these pathways at all,which is the reason why antibiotics do not work against viral infections.

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.

State whether the following statement is true or false:
The diseases which last for only short periods of time are called chronic diseases.