Why we taking (vitamin D)? especially today against Corona virus?

Explanation:

At least in theory, there may be something to these claims.

Nearly all immune cells have vitamin D receptors, showing vitamin D interacts with the immune system.

The active vitamin D hormone, calcitriol, helps regulate both the innate and adaptive immune systems, our first and second lines of defence against pathogens.

And vitamin D deficiency is associated with immune dysregulation, a breakdown or change in the control of immune system processes.

Many of the ways calcitriol affects the immune system are directly relevant to our ability to defend against viruses.

For example, calcitriol triggers the production of cathelicidin and other defensins – natural antivirals capable of preventing the virus from replicating and entering a cell.

Calcitriol can also increase the number of a particular type of immune cell (CD8+ T cells), which play a critical role in clearing acute viral infections (such as influenza) in the lungs.

i'm pretty sure it is letter c.) car

the enthalpy of formation of water is given as -285.8kj/mol, which states that the enthalpy of formation is negative.

negative enthalpy of formation indicates that the heat is released during the reaction process. the heat is released from reaction to the surroundings the enthalpy is expressed with a negative sign with the energy given out in the reaction process.

the formation of water takes place by giving out heat which is -285.8 kj/mol.