5) write a regular expression would zip code + 4 fields of the forms: - where x is any number but the last 4 digits could be missing. the dash at the end of the first 5 numbers will always be present and the field is delineated with spaces or tabs.

Following is the expression written in "Bash script" (mixture of commands):

^\d{5}(?:[-\s]\d{4})?$

Explanation:

                 (checking if a hyphen is present?)

he could use bold or bigger text just a suggestion.

it would be a. excessive network collisions or d. slow connectivity between devices those would be my answer.