the transition metals are elements with partially filled..?

Question

1.) p subshells
2.) d subshells
3.) s subshells
4.) f subshells

Answer 1

d subshells, as a general rule

Answer 2

2) d subshells.

Think of it this way. You already have the s and p subshells filled, and the f subshells don't come around until the lanthanide series.