PHP will help enhance his job prospects in the field.
C. PHP
Step-by-step explanation:
Since Walter has already associated computer degree, CompTIA is a basically IT knowledge courses which covers limited on web page development.
Microsoft Technology Associate: - it covers mostly operating system and covers MS office extra.
PHP: - It is web pages development programming languages. So Walter can do course on PHP
PageMaker:-it is a tools to use to manipulates with object and text, but not so used much on web pages
SAS Certified Base Programmer: - it is tools for doing analysis with help of R, python extra.