1. Surrender immediately: Civilian casualties will be minimized, but their country would likely be broken-up and the remainder turned into a satellite of Russia.
2. Dig-in and fight. Make it costly for the Russians to take the country, but use this war of attrition as a means of getting to the bargaining table. Pros: Likely a better political outcome than option # 1, but there will be a cost of death, injury and destruction. The danger of this approach is that they give Russia too much of a black eye and back Putin into demanding unconditional surrender.
3. Fight to the bloody end. Refuse to negotiate. Pros: They could end up with a better outcome than option # 2. Cons: They could end-up with a much worse political outcome than option #1 and suffer horrendous levels of death, injury and damage.