Emails are an important marketing communications tool because of all of the following reasons EXCEPT:

a$.$ They can be sent broadly when the company has customer contact information through purchasing.

b$.$ Customers who have not opted in will not respond to promotions.

c$.$ They can be sent to customers who have opted in$.$

d$.$ Customers can respond to promotional emails $($e$.$g$.,$ "Buy now, for $25\%$ off!"$).$