There are two important reasons that we must properly define the data type of a field.

a$.$ A data type tells the database what functions can be performed with the data and the proper amount of storage space to allocated for the data.

b$.$ All of the choices are correct

c$.$ None of the choices provided are correct

d$.$ There are data type standards used in the industry which are common for example Name which is text$(50)$ interpreted as data type text, field size $50$

e$.$ It is required for the development of a database and specifically keys for relationships