Final answer:
To get the peninsula in southern Ukraine, you need to add the letter 'a' to the word 'crime'. The resulting word is 'Crimea', which is a disputed territory between Ukraine and Russia.
Step-by-step explanation:
The letter you need to add to the word 'crime' to get a peninsula in southern Ukraine is a) Crimea. The Crimean Peninsula was annexed by Russia in 2014 and is now a disputed territory between Ukraine and Russia. This event was a significant conflict driven by Russia's desire for power and control over the region.