Tina, a technical analyst, is aiming for a promotion later this year. To increase her chances of securing a promotion, she enrolls in a certification program to develop her expertise in her current field of work. She becomes an expert in handling technical software and troubleshooting, an ability that she lacked before.

Identify the resource Tina invested in to achieve her financial goals.

a$.)$

Willingness to relocate

b$.)$

A formal network

c$.)$

Skill development

d$.)$

Health