From our initial setup, we can tell that 5 must be a t, since it cannot be r or s, and that 8 must be a t, because it can't be another s, and putting an r there would violate the r/t rule. So our initial setup is
_ R T _ _ _ S T
We can also determine what various things cannot be by virtue of what they are next to
_ R T R/S _ r/t S T
This setup let's us knock off a few answer choices right off the bat. It's impossible to have four or five ranch houses, if we made the three existing ranch house options all into Rs, neither of the two remaining slots could be ranches because they would both be next to a ranch. So, we can knock out D and E.
We can also immediately knock out B, since we already have two Ts. At that point, I would maybe test out the two remaining answer choices and since we can make a valid scenario with only one R, I would go with a, and not worry about c.
