What job or career field is C 35 in the active army?

Answer 1

In general it is an electronic and mechanical repair field

10–111. 35B—Land Combat Support System (LCSS) Test
Specialist (LCSS Test Spc), CMF 35

for more detail than you probably need see

https://134.11.61.26/CD4/Publications/DA/DA%20Pam/DA%20Pam%20611-21%2019990331.pdf