Answer:
OS, Os, oS, os
Explanation:
To do this, first we need to determine what the genotype of the Plant C offspring is. Since the parents are both true bred, this means that their offspring will get one allele of each parent, of each trait.
Here's a Punnett to help you there
OOSS x ooss
os os os os
OS OoSs OoSs OoSs OoSs
OS OoSs OoSs OoSs OoSs
OS OoSs OoSs OoSs OoSs
OS OoSs OoSs OoSs OoSs
So Plant C would have a genotype of OoSs.
A good trick to determining the gametes of a dihybrid, is the FOIL method. Just like in math, F- first, O-outside, I- inside, and L-Last
Look at the attachment to see the FOIL method: