Why is it a mistake to put email addresses of people who don't know each other in the "to: " field?

So they can know who it is going to . You cannot send an email without knowing who it goes to :)

Because you've revealed multiple people's email addresses, which can potentially expose them to spam emails, etc

Cprogram to find //perimeter of rectangle printf(" \n perimeter of rectangle \n"); printf(""); printf("\n enter width and length of the rectangle : "); scanf("%f%f", & width,& length); perimeter = 2 * (width + length); printf("perimeter of rectangle is: %.3f", perimeter);  

No you can not i had try